JP4209663B2 - Injection molding method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is an injection molding method in which a synthetic resin such as a melted plastic is injected into a confined mold, and then a cooled and solidified molded product is taken out by opening the mold to obtain a molded product as an object. And improvement of the apparatus.
[0002]
[Prior art]
In general, various injection molding methods and apparatuses have been proposed in order to obtain a relatively precise molded product from a synthetic resin such as plastic.
[0003]
In this conventional injection molding method and apparatus, the molten resin that has been preheated and applied with a preload through a runner (molten resin guide passage) formed in the mold is guided to the gate formed at the tip of the runner, The molten resin is injected and filled into the mold cavity from this gate.
[0004]
And after completion | finish of injection filling of molten resin, the said molten resin is solidified by cooling, Then, a metal mold | die is opened and a molded article is taken out from the inside of the cavity formed in the said metal mold | die by this.
[0005]
FIG. 13 is a conceptual cross-sectional view of the main part of the conventional injection molding apparatus 1 described above, and in particular, a molded product having a substantially U-shaped cross section (for example, a cylindrical lid) formed with a peripheral wall portion larger than the plate thickness of the molded product. 1 shows an injection molding apparatus 1 for molding a molded article such as a body.
[0006]
The injection molding apparatus 1 includes an upper mold 3 in which a cavity 2 having a substantially U-shaped cross section is formed, a lower mold 4 in which a core to be inserted into the cavity 2 is formed, and the cavity 2, a runner 5 that guides the molten resin that has been preheated and given a preload, and a gate 6 that injects the molten resin guided through the runner 5 into the cavity 2.
[0007]
Among them, the runner 5 for guiding the molten resin is formed between the upper and lower molds 3 and 4, and the gate 6 is located on the side of the cavity 2 having a substantially U-shaped cross section, that is, on the outer peripheral edge 2 a of the cavity 2. It has been formed.
[0008]
In FIG. 13, reference numeral 8 denotes an ejector pin that takes out a molded product from the cavity 2, and reference numeral 9 denotes an ejector pin that takes out the molten resin cooled and solidified in the runner 5.
[0009]
Next, the operation of the above-described conventional injection molding apparatus 1 will be described.
[0010]
As shown by the arrows in FIG. 14, the molten resin 10 that has been preheated and preloaded is injected and filled from the gate 6 into the cavity 2 through the runner 5. When the molten resin 10 is cooled and solidified in the cavity 2, a cylindrical molded article 11 having a substantially U-shaped cross section is formed in the cavity 2.
[0011]
In this way, when the molten resin injected and filled in the cavity 2 is cooled and solidified to form the cylindrical molded article 11, the space between the upper mold 2 and the lower mold 4 is formed as shown in FIG. After that, the ejector pins 8 and 9 are simultaneously raised as indicated by arrows.
[0012]
Then, together with the molten resin 10 cooled and solidified in the runner 5, a cylindrical molded product 11 having a substantially U-shaped cross section is taken out from the cavity 2.
[0013]
[Problems to be solved by the invention]
By the way, according to the conventional injection molding method and apparatus 1 described above, as shown in FIG. 15, the ejector pins 8 and 9 are raised to form a cylindrical molded article 11 having a substantially U-shaped cross section in the mold. At the same time, the molten resin 10 cooled and solidified in the runner 5 is also taken out in a state of adhering to the molded product 11.
[0014]
Therefore, conventionally, in the subsequent process, an operation of removing the molten resin 10 cooled and solidified in the runner 5 from the molded product 11 is performed. Then, as shown in FIG. 16, the outer peripheral surface of the molded product 11 that is most easily touched by human eyes. 11a, that is, burrs and gate traces 12 are formed at positions facing the gates 6, so these must also be removed in a later process, and the manufacturing cost of the molded article 11 having a substantially U-shaped cross section is extremely high. The difficulty that arises.
[0015]
In view of the above-described circumstances, the present invention provides an injection molding method and apparatus that prevents generation of burrs and gate marks due to gates on the outer peripheral surface when a molded article having a substantially U-shaped cross section is injection molded. With the goal.
[0016]
[Means for Solving the Problems]
In order to solve the above-described problems, in the present invention, the molten resin that has been preloaded is guided to the gate through the runner, and the molten resin is inserted into the cavity having a substantially U-shaped cross section formed in the mold from the gate. In the injection molding apparatus, the molten resin injected into the cavity is cooled and solidified to obtain a molded product having a substantially U-shaped cross section. A slide piece which is formed at a position facing the inner peripheral surface of the tee and is slidably supported by a part of the runner with respect to the mold, and is in a direction perpendicular to the traveling direction of the runner A cross-section substantially base that is formed into a horizontally slidable slide piece, and the cross-sectional shape of a part of the runner formed on the slide piece increases toward the runner side. Formed in, during the die cutting of the molten resin was cooled and solidified in said runner, said slide piece is moved, the runner portion formed on the sliding pieces so as to peel from the cooled and solidified molten resin It is characterized by.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of an injection molding method and apparatus according to the present invention will be described in detail.
[0018]
FIG. 1 is a conceptual cross-sectional view of an injection molding apparatus 20 for carrying out the injection molding method according to the present invention, and the same parts as those in FIG.
[0019]
The injection molding apparatus 20 (hereinafter simply referred to as “apparatus”) also includes an upper mold 21 having a substantially U-shaped cavity 2 formed therein, a lower mold 22 having a core formed therein, and the cavity 2. The runner 23 guides the molten resin that has been preheated and given a preload, and the gate 24 that injects the molten resin guided through the runner 23 into the cavity 2.
[0020]
Among these, the gate 24 is formed in the lower mold 22 at a position (core portion) facing the inner peripheral surface 2b of the cavity 2 having a substantially U-shaped cross section.
[0021]
On the other hand, the runner 23 communicating with the gate 24 is a substantially L-shaped plane that is slidably supported with respect to the upper and lower molds 21 and 22 and the lower mold 22 as shown in FIG. The slide piece 25 is formed. As shown in FIG. 2, the slide piece 25 is slidable in a vertical direction in the rectangular hole 22a formed in the core portion of the lower mold 22 in the drawing.
[0022]
In addition, the part of the runners passing through the slide piece 25 in the above-described runner 23 shown in FIG. 1, that is, the cross-sectional shape 23b of the runner portion 23a is, as shown in FIG. In consideration of the above, the cross section is formed in a substantially trapezoidal shape, and the portion that comes into contact with the lower mold 22, that is, the one side surface 23 c to be punched is released.
[0023]
When such a slide piece 25 moves downward along the hole 22a in FIG. 2, the slide piece 25 comes into contact with the lower end of the hole 22a and stops as shown in FIG.
[0024]
Thus, when the slide piece 25 moves down the drawing along the hole 22a and stops in contact with the lower end of the hole 22a, the slide piece of the runner 23 as shown in FIG. The runner portion 23 a passing through 25 moves and the runner portion 23 a is lost from the course of the runner 23. In FIG. 4, reference numeral 27 denotes a guide hole formed in the lower mold 22 into which the slide piece 25 is slidably fitted.
[0025]
Next, the above-described injection molding method according to the present invention will be described based on the action of the injection molding apparatus 20, and the configuration will be described in more detail.
[0026]
As shown in FIG. 5, when the molten resin 10 that has been heated and preloaded is injected through the runner 23 as indicated by an arrow C, the molten resin 10 passes through the runner portion 23 a formed on the slide piece 25, Thereafter, the cavity 2 is injected and filled from the gate 24 formed in the lower mold 22 at a position facing the inner peripheral surface 2b of the cavity 2 having a substantially U-shaped cross section.
[0027]
The injected molten resin 10 passes through a runner portion 23a having a trapezoidal cross section in the slide piece 25 as shown in FIG. 6 shown in the CC sectional view of FIG.
[0028]
Then, when the molten resin 10 is cooled and solidified in the cavity 2, as shown in FIG. 5, a cylindrical molded product 11 having a substantially U-shaped cross section is formed in the cavity 2.
[0029]
Thus, after the molten resin injected and filled in the cavity 2 is cooled and solidified to form the cylindrical molded article 11, the upper mold 21 and the lower mold 22 are separated from each other to perform gate cutting. Thereafter, when the ejector pins 8 and 9 are raised, the cylindrical molded article 11 having a substantially U-shaped cross section is taken out from the cavity 2.
[0030]
At the time of this removal, burrs and gate traces 12 are formed on the portion of the molded product 11 facing the gate 24 shown in FIG. However, since this portion 11b is a portion that cannot be seen from the external appearance, operations such as deleting burrs and gate traces 12 of the molded product 11 in a subsequent process as in the conventional product are completely unnecessary.
[0031]
On the other hand, after the molded product 11 is taken out, the molten resin 10 injected into the runner 23 and cooled and solidified must be simultaneously removed from the mold.
[0032]
Therefore, the injection molding apparatus 20 of the present invention takes out the molten resin 10 cooled and solidified in the runner 23 as follows.
[0033]
First, when the slide piece 25 is moved as indicated by an arrow E from the stop position of the slide piece 25 shown in FIG. 6, the slide piece 25 comes into contact with the lower end of the hole 22a and stops as shown in FIG.
[0034]
As shown in FIG. 7, when the slide piece 25 is moved to a position where it comes into contact with the lower end of the hole 22a, cooling is performed from the runner portion 23a having a trapezoidal cross section formed in consideration of the draft of the molten resin 10. The solidified molten resin 10 is peeled off and extracted from the runner portion 23a.
[0035]
Then, as shown in the EE cross section of FIG. 7, the molten resin 10 cooled and solidified in the runner 23 is adjacent to the gate 24 as shown in FIG. The molten resin 10 at the tip portion 23b of the runner 23 adheres to the portion, but the molten resin 10a in the runner portion 23a formed on the slide piece 25 forming the runner 23 therebetween is the ride shown in FIG. It has already peeled from the runner part 23a by the movement of the piece 25. Therefore, the frictional force acting between the molten resin 10 and the runner 23 when the molten resin 10 cooled and solidified in the runner 23 is extracted from the runner 23 is significantly reduced.
[0036]
For this reason, as shown in FIG. 9, after the upper die 21 is separated from the lower die 22 and the ejector pins 8 and 9 are simultaneously raised as shown by arrows, the tip of the runner 23 is added to the gate cut. The molten resin 10 in the portion 23 b is easily extracted from the tip portion 23 b of the runner 23.
[0037]
Thereafter, when the ejector pins 8 and 9 are further raised from the positions of the ejector pins 8 and 9 in FIG. 9, runners run from the guide holes 27 into which the slide pieces 25 are slidably inserted as shown in FIGS. 10 and 11. All the molten resin 10 cooled and solidified in 23 is taken out.
[0038]
Thereafter, when the ejector pins 8 and 9, the slide piece 25, the upper mold 21 and the like are returned to the initial positions in FIG. 1, the injection molding apparatus 20 returns to the standby position for injection molding the next product.
[0039]
In the injection molding method of the present invention, as shown in FIG. 1, the gate 24 may be formed at a position facing the inner peripheral surface 2b of the cavity 2 having a substantially U-shaped cross section. Without being limited to the example, the gate 24 is formed on the inner peripheral surface 2b facing the outer peripheral edge 2a of the cavity 2 as shown in FIG. May be.
[0040]
In the above embodiment, the cross-sectional shape 23b of the runner portion 23a is formed in a substantially trapezoidal cross section. However, the present invention is not limited to the above-described embodiment, and the draft of the molten resin that has been cooled and solidified is taken into consideration. For example, a polygonal shape such as a triangular shape may be used.
[0041]
【The invention's effect】
As described above, according to the injection molding method of the present invention, the gate is formed so as to face the inner peripheral surface of the cavity having a substantially U-shaped cross section, and the molten resin is formed to have a substantially U-shaped cross section from the gate. Because it is injected into the cavity, there are no gate burrs or gate traces on the outer peripheral surface of the molded product, which eliminates the need to remove burrs and gate traces from the molded product in the subsequent process. The manufacturing cost of a molded product having a substantially U-shaped cross section can be significantly reduced and provided at a low cost.
[0042]
In the injection molding apparatus of the present invention, a part of the runner that guides the molten resin to the gate is formed on a slide piece that is slidably supported with respect to the mold, and the slide piece is moved when the mold is removed. Since the runner part formed on the slide piece is peeled off from the molten resin that has been cooled and solidified inside, when the molten resin that has been cooled and solidified in the runner is die-cut, the gap between the runner and the cooled and solidified molten resin Therefore, the molten resin cooled and solidified can be easily removed from the runner.
[Brief description of the drawings]
FIG. 1 is a fragmentary conceptual sectional view of an injection molding apparatus for carrying out an injection molding method according to the present invention.
FIG. 2 is a cross-sectional view taken along line AA in FIG.
FIG. 3 is a diagram showing the action of a slide piece.
4 is a BB cross-sectional view of FIG. 3;
FIG. 5 is a conceptual cross-sectional view showing the operation of the injection molding apparatus of the present invention.
6 is a CC cross-sectional view of FIG. 5;
7 is a CC cross-sectional view of FIG. 5 showing the action of the slide piece. FIG.
8 is a cross-sectional view taken along the line EE in FIG. 7;
FIG. 9 is a conceptual cross-sectional view showing the operation of the injection molding apparatus of the present invention.
FIG. 10 is a conceptual cross-sectional view showing the operation of the injection molding apparatus of the present invention.
FIG. 11 is a conceptual cross-sectional view showing the operation of the injection molding apparatus of the present invention.
FIG. 12 is a conceptual sectional view of a principal part of an injection molding apparatus showing another embodiment. FIG. 13 is a conceptual sectional view of a conventional injection molding apparatus.
FIG. 14 is a conceptual cross-sectional view showing the operation of a conventional injection molding apparatus.
FIG. 15 is a conceptual cross-sectional view showing the operation of a conventional injection molding apparatus.
FIG. 16 is a cross-sectional view of a molded product obtained by a conventional injection molding apparatus.
[Explanation of symbols]
2 ... cavity 2b ... inner peripheral surface 10 of the cavity ... melted resin 11 ... molded product 20 having a substantially U-shaped cross section ... injection molding apparatus 21, 22 ... mold 23 ... runner 23a ... runner portion 24 ... gate 25 ... Slide piece

Claims (1)

The pre-pressed molten resin was guided to the gate through the runner, and the molten resin was injected from the gate into a cavity having a substantially U-shaped cross section formed in the mold, and injected into the cavity. In an injection molding apparatus in which a molten resin is cooled and solidified to obtain a molded product having a substantially U-shaped cross section,
The gate is formed at a position facing the inner peripheral surface of the cavity having a substantially U-shaped cross section, and
A part of the runner is slidably supported with respect to the mold , and is formed into a slide piece that is perpendicular to the traveling direction of the runner and that is slidable horizontally. Form a partial cross-sectional shape of the runner formed on the slide piece into a substantially trapezoidal cross section in which the opening cross section becomes larger toward the runner side,
When the molten resin cooled and solidified in the runner is removed from the mold, the slide piece is moved so that the runner portion formed on the slide piece is separated from the cooled and solidified molten resin. Injection molding equipment.

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