JPH06297511A - Method and device for injection molding of product having through-hole - Google Patents

Abstract

PURPOSE:To eliminate the need for secondary processing, to prevent generation of material other than a product and to shorten time necessary until mold release by inserting a center pin into the center part of a cavity and forming a through-hole in the center part of resin being in a molten state and closing the opening of a nozzle by the tip of the center pin. CONSTITUTION:Thermoplastic resin is supplied to a hot runner nozzle and injected from a gate of the tip of the nozzle to the center part of a cavity 12. When resin is still in a molten state, a projection rod 18 is extended into a hole and a center pin 13 is inserted into the center part of the cavity 12 through a slide plate 15. The center part of resin being in the molten state is penetrated by the center pin 13. The tip of the center pin 13 is extended to close the gate of the hot runner nozzle. The center hole of a through-hole is formed in a product by the actuation. Then a bottom plate 4 of a movable side is retreated and the retainer plate 3 of a fixed side and the retainer plate 6 of a movable side are separated from each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method for a product having a disk-like or elliptical outer shape such as a rotating plate or a gear and a through hole formed in the center thereof, and an apparatus therefor. .

[0002]

2. Description of the Related Art Conventionally, a direct gate method has been generally used as a method for injection molding a gear. According to this method, molten resin is supplied to the cavity from the sprue, and from the viewpoint of ensuring the dimensional accuracy of the product, the resin flow is injected from the gate to the center of the cavity and flows radially from this gate. , Were oriented on average. After that, a pressure-holding process to prevent backflow of the resin from the gate and to supplement the volume associated with shrinkage, a process to cool the molten resin, and finally a process to take out the product from the cavity It was a transition.

[0003]

However, in the direct gate method, after the sprue portion is solidified, the product is released together with the solidified portion in the spray portion.
Not only is it necessary to carry out a secondary process of cutting the sprue portion and the product to remove the sprue portion, but materials other than the product are generated. Further, when the diameter of the sprue portion is a product, that is, in the case of a structure that is thicker than the thickness of the cavity, it takes time for the sprue portion to solidify in the cooling step, and mold release cannot be performed until then.
The mass productivity was low.

Therefore, an object of the present invention is to provide an injection molding method and an apparatus therefor, in which secondary processing after molding is not necessary, materials other than products are not generated, and the time until demolding can be shortened. is there.

[0005]

The first feature of the present invention is to:
The center pin is inserted into the center of the cavity to penetrate the center of the molten resin to form a through hole, and the tip of the center pin closes the opening of the hot runner nozzle.

A second feature of the present invention is that the hot runner, the heating means, the cavity, the center pin,
Composed of an ejector pin, the hot runner has a hot runner nozzle at the tip,
The heating means is for holding the molten state of the thermoplastic resin passing through the hot runner, the center pin is movably provided on the movable side mold plate, the center pin and the ejector Each of the pins is provided with a movement driving means for entering the cavity, and the tip of the hot runner nozzle is
The center pin is open at one center of the cavity, the center pin is capable of penetrating into the other center of the cavity, and is provided so as to face the tip of the hot runner nozzle. Has a tip capable of closing the tip opening of the hot runner nozzle.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, a spacer block 2 and a fixed side mold plate 3 are integrally provided on a fixed side mounting plate 1 located on one side (upper side of the drawing). Further, the movable side mounting plate 4 located on the other side includes a spacer block 5 and a movable side template plate 6.
And are provided integrally.

A locate ring 7 is fixed to the outer surface of the fixed side mounting plate 1 with a screw.
The nozzle 8 is located. A manifold 9 is provided in the hollow portion of the spacer block 2, and a hot runner 10 is divided into two parts to penetrate the manifold, and a nozzle 8 is joined to the rear end of the hot runner.
The tip is a hot runner nozzle 10a. Further, the manifold 9 is provided with a heater 11 as a heating means, and this heater is for holding the molten state of the thermoplastic resin located in the hot runner.

Between the fixed side mold plate 3 and the movable side mold plate 6,
A cavity 12 is formed, and a center pin 13 and two ejector pins 14,
14 and 14 are movably provided in the vertical direction of the drawing so as to be able to enter the cavity, and the center pin and the ejector pin are provided with movement driving means. The structure of the movement driving means for the center pin 13 is that a slide plate 15 consisting of two plates 15a, 15a is provided in the spacer block 5, and the base end portion of this center pin is fixed to this slide plate. A protruding rod 16 is connected to the rear surface of the sliding plate. Further, the structure of the movement driving means of the ejector pins 14 and 14 is such that an ejector plate 17 composed of two plates 17a and 17b is provided in the spacer block 5, and this ejector plate has a base end portion of the ejector pin. Is fixed, and a protruding sleeve 18 is connected to the back surface of the ejector plate.

The tip opening (gate) of the hot runner nozzle 10a is opened at the center of one of the cavities 12 (above the drawing), and the center pin 13 is provided.
Is slidably provided toward the center of the other side (downward in the drawing) of the cavity, and is provided so as to face the gate of the hot runner nozzle. Further, since the diameter of the center pin 13 is the same as the inner diameter of the tip opening of the hot runner nozzle 10a, this opening can be closed.

Further, in the fixed side spacer block 2 and the fixed side template 3, holes 19 for supplying cooling water are formed at positions close to the manifold 9. Further, on the movable side, two return pins 20 and 21 are provided in a state of penetrating the movable side mold plate 6, and the base end portion of one of the return pins 20 is fixed to the ejector plate 17. A spring 22 is provided with the pin wound. The base end of the other return pin 21 has a sliding plate 1
5, the spring 23 is provided in a state where the return pin is wound. A guide pin 24 is provided on the movable spacer block 5 so as to project toward the fixed side, and the tip of this guide pin is fitted to a guide bush 25 provided on the fixed side.

Next, the injection molding method according to the present invention will be described with reference to FIGS.

In the state shown in FIG. 1, the molten thermoplastic resin is supplied from the nozzle 8 to the hot runner nozzle 10a via the hot runner 10, and further injected from the center of the cavity 12 from the gate at the tip of the nozzle. It At this time, since the resin is radially and averagely oriented from the center of the cavity 12, no weld line is generated. In addition, the heater 11 allows the hot runner 1
The resin in 0 is kept in a molten state. After that, the process of holding pressure is started, and by this holding pressure, the injection pressure is maintained so that the molten thermoplastic resin does not flow backward from the gate of the hot runner nozzle 10a. Replenish the volume associated with shrinkage during cooling. This is the state shown in FIG. At this time, the molten resin in the cavity is heated to a predetermined temperature by the cooling water supplied into the holes 19, 19.

During this pressure-holding step (or cooling step), when the resin is still in a molten state, the projecting rod 18 is extended, and the center pin 12 is caved through the sliding plate 15 as shown in FIG. It is inserted in the central part of 12 and penetrates the central part of the resin in a molten state. Further, the tip of the center pin 13 is stretched to form the hot runner nozzle 10
It is fitted to the gate of a and the gate is closed. By this operation, the central hole Aa of the through hole is formed in the product A.

Next, by retracting the movable side mounting plate 4, the space between the fixed side mold plate 3 and the movable side mold plate 6 is opened, and as shown in FIG.
To the state of. At this time, the hot runner nozzle 10a
Although the tip of the center pin 13 is separated from the opening of the above, since the pressure is reduced in the nozzle 8, the resin does not flow out from the gate of this hot runner nozzle.

Then, the protruding sleeve 18 is stretched,
As shown in FIG. 5, the ejector pins 14 and 14 are projected from the movable side mold plate 6 through the ejector plate 17 to release the product A from the cavity 12.

[0018]

According to the present invention, since the resin is injected from the center of the cavity from the hot runner nozzle, a weld line does not occur, a product having a through hole can be molded with high accuracy, and post-processing of a gate mark is performed. Is unnecessary. Further, unlike the conventional case, since there is no secondary processing for cutting the sprue portion and a hot runner is used, materials other than the product are not generated, and the time until the product is released can be shortened.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the overall configuration.

FIG. 2 is an enlarged cross-sectional view showing a molding process.

FIG. 3 is an enlarged cross-sectional view showing a molding process.

FIG. 4 is an enlarged cross-sectional view showing a molding process.

FIG. 5 is an enlarged cross-sectional view showing a molding process.

[Explanation of symbols]

3 Fixed-side mold plate 6 Movable-side mold plate 10 Hot runner 10a Hot runner nozzle 11 Heating means (heater) 12 Cavity 13 Center pin 14 Ejector pin 15 Center pin movement drive means (sliding plate) 16 Center pin movement drive means (Projection rod) 17 Ejector pin movement drive means (ejector plate) 18 Ejector pin movement drive means (projection sleeve) A Product Aa Through hole

Claims (2)

[Claims] 1. A step of injecting a molten thermoplastic resin from a hot runner nozzle into the cavity from a central portion of the cavity, a step of holding a pressure thereafter, a step of cooling to solidify the product, and a step of taking out the product from the cavity. In the injection molding method, which comprises a step, a center pin is inserted into the center of the cavity to form a through hole through the center of the resin in a molten state, and the tip of the center pin is the opening of the nozzle. Injection molding method for products with through-holes characterized by closing 2. A hot runner, a heating means, a cavity, a center pin, and an ejector pin, wherein the hot runner has a hot runner nozzle at its tip, and the heating means includes a hot runner inside the hot runner. It is for holding the molten state of the thermoplastic resin passing therethrough, the cavity is formed between the fixed side mold plate and the movable side mold plate, and the center pin is the movable side mold plate. The plate is movably provided, and the center pin and the ejector pin are provided with movement driving means for intruding into the cavity, and the tip of the hot runner nozzle is at the center of one of the cavities. The center pin is capable of penetrating into the center of the other side of the cavity, and the center pin is open. A state opposite to the tip end of the runner nozzle, the tip of the center pin, the injection molding apparatus of a product having a through-hole, characterized in that it is capable closing the tip opening of the hot runner nozzle.