JPH0159089B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of injection molding a covering part by passing a resin material from the upper surface of the insert to the middle of the circumference into the cavity of a mold in which an insert is set, and in particular, the method of injection molding a covering part between an insert and a covering part. This is a molding method suitable for molding two-color molded products with different colors.

Injection molding here includes not only injection molding and transfer molding but also reaction injection molding.

Conventionally, as shown in FIG. 1, a sprue, a gate, etc. (not shown) are inserted into a metal cavity 4 (fixed type 2, movable type 3) in which an insert 1 is set, from the top surface of the insert 1 to the middle of the circumference. When molding the covering part 5 by passing the resin material injected through the insert 1, burrs 6 may occur at the boundary between the insert 1 circumferential surface and the covering part 5 (Fig. 2), and the insert 1
The peripheral surface may be coated down to the lower part (third
(Figure), the boundary line (parting line) between the insert 1 and the covering part 5 did not appear clearly, and especially when the insert 1 and the covering part 5 were different colors, the design was adversely affected. The reason for this is that since the insert 1 is also usually molded from a synthetic resin material, there is variation in the shrinkage of the insert 1 after molding, and also from the viewpoint of workability when setting the insert 1 into the mold (fixed mold 2).
This is because the insert 1 and the fixed mold 2 are designed with a clearance fit, so that a gap is likely to be created between the insert 1 and the fixed mold 2 through which resin can flow.

In view of the above, an object of the present invention is to provide a method for injection molding a product containing an insert, in which a boundary line between the circumferential surface of the insert and the covering portion is clearly formed.

The method for molding the insert-containing product of this invention is as follows:
A step is formed at the boundary between the circumferential surface of the insert and the covering section, and a slide core with a protrusion on the inner wall that engages with the step presses the outer circumferential surface of the insert below the step, thereby molding the resin material into the cavity. The above object is achieved by injecting the resin into the coating and forming the covering part.

Hereinafter, the method of the present invention will be explained based on illustrated examples.

Figures 4 and 5 show an example of a mold used in the method of the present invention, with the left side showing the mold closed and the right side showing the mold opening.

In the insert setting convex part 12 of the fixed mold 11,
After setting the insert 14 having the stepped portion 13 formed on the circumferential surface at the boundary with the covering portion, the mold is closed. Then, the slide core 16, which has a protrusion 15 on its inner wall that can engage with the stepped portion 13, moves toward the insert 14 against the force of the spring 18 due to the tapered concave surface of the movable mold 17, and presses the outer peripheral surface of the insert 14. I come to do it. Naturally, the insert 14 has a thickness such that it is tightly fitted at the front dead center position of the slide core 16. Next, sprues, gates, etc. (not shown)
When the resin material is injected into the cavity 19 through the slide core, the protrusion 15 of the slide core engages with the step 13 of the insert, and the outer circumferential surface of the insert 14 below the step is pressed by the slide core 16. Therefore, the stepped portion 13 of the insert is made of resin material.
That is, it does not extend to the peripheral surface of the insert below the boundary line forming area between the covering portion 20 and the insert 14. Further, since a boundary groove is formed by the protruding strip 15 of the slide core at the boundary between the covering portion 20 and the insert 14, the boundary becomes clear.

6 and 7 show another mold used in the method of the present invention, in which a slide core 21 is linked with an ejector plate 23 via a connecting rod 22 to press the lower outer peripheral surface of the stepped portion 13 of the insert 14. It was designed to do so. In this case, when the mold is closed, the protrusions 24 of the slide core also act to press the insert step 13, ensuring that the resin material is applied to the step 13 more reliably.
It can prevent it from turning downward. In addition, 25 is ejecta pin.

The injection molding method for insert products of this invention is as follows:
Because of the method described above, there is almost no risk of the resin material going around below the boundary line forming area between the covering part and the insert during injection molding, and a boundary groove is formed on the circumferential surface of the product, so that the boundary groove on the insert circumferential surface is The boundary line with the covering part appears very clearly. Therefore, when applied to a two-color molded product in which the insert covering portion is a different color, a product with excellent design can be obtained.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the main part of the mold when the mold is closed in the conventional molding method, Figures 2 and 3 are partial cross-sectional views of the product showing defective states that occur in the conventional molding method, and Figure 4 is the main part of the mold when the mold is closed. FIG. 5 is a plan view of the fixed die side of the mold used in the molding method of the invention, FIG. 5 is a sectional view of the main part of the mold in FIG. 4, and FIG. FIG. 7 is a plan view of the fixed mold side, and is a sectional view of the main part of the mold in FIG. 6. 1... insert, 2... fixed type, 3... movable type, 4... cavity, 5... covering part, 11...
Fixed type, 13...Stepped part, 14...Insert, 1
5, 24... Convex strip, 16, 21... Slide core, 17... Movable type, 19... Cavity, 20
...covering part.

Claims (1)

[Scope of Claims] 1. A method of injection molding a coating portion by wrapping a resin material from the upper surface of the insert to the middle of the circumferential surface of the mold cavity in which the insert is set, wherein: A step is formed at the part, and a slide core having a protrusion on the inner wall that engages with the step presses the lower outer peripheral surface of the step of the insert to inject a resin material into the cavity to form the covering portion. A method for molding a product with an insert, which is characterized by molding.