JPH02172B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <<Field of the Invention>> This invention relates to improvements in mold apparatus used for injection molding of thermoplastic resins.

≪Prior art and its problems≫ Injection molding is a molding method in which molten resin is injected into a mold cavity using a plunger, solidified in the mold, and then the molded product is taken out from the mold. It is.

The mold apparatus used for this injection molding is shown in FIG. This device a consists of a sprue c that receives the molten resin from a plunger (not shown) for introducing the molten resin into the cavity b, a cavity sprue or gate d, and a runner e that runs from the sprue c to the gate d. Cage, cavity b
The molded product f solidified inside is taken out from the mold g with unnecessary resin such as gates d and runners e attached, so in order to remove unnecessary parts attached to the molded product f, after molding A gate cut was being performed (the cut line is shown as a broken line in the drawing).
Therefore, there was a problem in that the work efficiency was poor because the cutting process required many man-hours.

Recently, as an attempt to eliminate this gate cut, a nose gate system as shown in FIG. 6, for example, has been proposed. In this method, after molding the molded product f, the tip j of the gate d is set at an extreme point so that when the molded product ejection pin h and the gate ejection pin i are ejected, the tip j of the gate d and the molded product f are cut. It is formed thinly.

However, although the gate cutting process can be omitted with this nose gate method, as mentioned above, the gate d is extremely thin, so the injection pressure during injection molding must be high, which causes sink marks. There were drawbacks such as easily damaging the appearance of the product and also causing problems in terms of dimensional accuracy.

≪Object of the Invention≫ This invention was made in view of the above-mentioned circumstances, and its purpose is to provide a method for injection molding that eliminates the gate cutting process, significantly reduces the number of man-hours, and that can reliably prevent sink marks after molding. Our goal is to provide mold equipment.

<<Configuration and Effects of the Invention>> In order to achieve the above-mentioned object, the mold device according to the present invention includes a cavity side mold, a core side mold,
A molded product ejecting pin disposed in the core side mold, an ejecting pin for ejecting a gate and a runner, a cavity formed by the closed molds, and a gate and a runner for injecting molten resin into the cavity. In the injection mold device, the molded product ejecting pin is formed to have a large diameter at the top and a small diameter at the bottom, and
A recess is provided below the tip of the gate between the outer peripheral surface of the large diameter part of the molded product ejecting pin and the core side mold, and when the molded product ejecting pin, gate, and runner ejecting pin rise, As the resin filled in the recess remains in the core side mold, the gate tip and the molded product are automatically cut, and as both ejector pins rise, the molded product ejector pin is placed on the side of the recess. When the small diameter portion is located, the remaining resin in the recess enters the gap formed between the recess and the outer circumferential surface of the molded product ejection pin, and due to the elastic restoration of the resin, the tip of the gate is pushed into the core side mold. be canceled from.

In this way, the molded product and gate are automatically cut, and unnecessary resin such as gates and runners can be easily removed, which not only greatly reduces man-hours, but also enables fully automatic molding. There is. In addition, mold processing is easy, and since the tip of the gate is not formed to be extremely thin like conventional nose gates, it has various effects such as suppressing the occurrence of sink marks and producing a molded product with a satisfactory appearance. has.

<<Description of Embodiment>> An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a longitudinal cross-sectional view of the mold apparatus of the present application showing the state during molding, and FIGS. 2 to 4 are explanatory views when demolding a molded product from the mold apparatus.

In the drawings, reference numeral 1 denotes a core-side mold, and a molded product ejection pin 3 and an ejection pin 4 are installed inside the core-side mold. A cavity 5 is formed by the core side mold 1 and the cavity side mold 2, and molten resin from a plunger and sprue (not shown) is introduced into the cavity 5 via a runner 6 and a gate 7, and the mold 1 , 2. Furthermore, a recess 8 is provided below the tip 7a of the gate 7. Specifically, this recess 8 is located between the outer peripheral surface of the molded product ejecting pin 3 and the core side mold 1.
It is formed by Kubomi 9.

The molded product ejecting pin 3 is composed of an upper portion 3a having a large diameter and a lower portion 3b having a small diameter.

Next, the process of demolding the molded product will be described based on FIGS. 2 to 4.

FIG. 2 shows a state in which the molded product ejection pin 3, the gate, and the runner ejection pin 4 are slightly raised after the molded product 10 is molded. At this time, the molded product 10 is pushed up by the molded product ejection pin 3, but the resin 11 filled and solidified in the recess 8 formed at the tip 7a of the gate 7 is pushed up by the hollow 9 of the core side mold 1.
remain within. Therefore, the molded product 10 and the gate 7, which were connected in FIG. 1, are automatically disconnected. Note that the molded product ejection pin 3 and the burr ejection pin 4 are interlocked.

FIG. 3 further shows the ejector pins 3 and 4 in a raised state. As is clear from the drawing, on the side of the recess 9, that is, the recess 8 of the core side mold 1,
The lower part 3b of the molded product ejection pin 3 is located. The lower part 3b of this ejecting pin 3 is the upper part 3a
Since the ejector pin 3 is formed to have a smaller diameter than the recess 8 , a gap 12 is created between the recess 8 and the outer circumferential surface of the ejector pin 3 . Therefore, the resin 11 remaining in the recess 8
Due to the elastic restoring action of the resin, it is released from the core-side mold and enters the void 12.

As shown in FIG. 4, the molding part 10, the runner 6, and the gate 7 are held by the molded product ejecting pin 3, the gate, and the runner ejecting pin 4, respectively, and are just waiting to be taken out from the mold device. state.

[Brief explanation of drawings]

1 to 4 show an embodiment of the injection molding device according to the present invention, FIG. 1 is a vertical cross-sectional view of the molding device of the present application during molding, and FIGS. 2 to 4 3A and 3B are vertical cross-sectional views each illustrating a demolding process after molding. FIGS. 5 and 6 are longitudinal cross-sectional views of conventional injection mold apparatuses, respectively. 1...Core side mold, 2...Cavity side mold,
3... Molded product ejection pin, 4... Gate, runner ejector pin, 5... Cavity, 6... Runner, 7... Gate, 8... Recess, 9... Hole, 10... Molded product, 11... ...Resin, 12...Void.

Claims (1)

[Claims] 1. A cavity formed by a cavity side mold, a core side mold, a molded product ejection pin disposed in the core side mold, an ejection pin for ejecting a gate and a runner, and a closed mold of both molds. In the injection mold apparatus, the molded product ejecting pin is formed to have a large diameter at the top and a small diameter at the bottom, and a gate for injecting molten resin into the cavity, and a runner. A recess is provided below the tip of the molded product ejection pin between the outer circumferential surface of the large diameter part and the core side mold, and when the molded product ejection pin, gate, and runner ejection pin are raised, the recess is As the resin filled inside remains in the core side mold, the gate tip and the molded product are automatically cut off, and as both ejector pins rise, the small diameter part of the molded product ejector pin is placed on the side of the recess. When positioned, the remaining resin in the recess enters the gap formed between the recess and the outer peripheral surface of the molded product ejection pin, and the elastic restoration of the resin causes the tip of the gate to be released from the core-side mold. An injection mold device characterized by: