JPS63319114A - Injection molding - Google Patents

Abstract

PURPOSE:To make it possible to easily cut off the runner part of soft resin from a molded item at its gate by a method wherein the runner part of the soft resin is put on rigid resin, when the molded item having the construction consisting of two layers or rigid resin layer and soft resin layer is ejected with ejector pins. CONSTITUTION:The release of a molded item 10 is done by the simultaneous actions of ejector pins 7a and 7b caused by opening a retainer plate 1 and a movable retainer plate 2 or, concretely by the abutting of the ejector pins 7a against the runner part 4a of rigid resin and their ejection in the opening direction of a mold and by the abutting of the ejector pins 7b against the molded item 10 and their ejection in the opening direction of the mold. Since the runner part 4b of soft resin fuses integrally with the runner part 4a of the rigid resin, almost no elongation of the runner part 4b occurs even when tensile force is applied, resulting in cutting off the runner part 4b from a gate at the corner extending from said runner part 4b in the gate. Needless to say, at this time, the runner part 4a of the rigid resin is simultaneously cut off at the gate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an injection molding method for molding a resin molded article having a two-layer structure of a hard resin layer and a soft resin layer by injection molding.

[Background of the Invention] This type of conventional injection molding method involves forming a hard resin layer using a hard resin material such as polycarbonate or ABS.
a primary molding step of molding the next molded product by injection molding;
The secondary molding process consists of forming a soft resin layer by injection molding a soft resin material such as urethane elastomer on the surface of the next molded product, and is carried out using a mold as shown in Figure 3. ing.

Reference numeral 1 designates a fixed mold plate, and 2 designates a movable mold plate. In the fixed mold plate 1, a cavity 6a for primary molding and a cavity 6b for secondary molding are formed symmetrically with respect to the center line °C. At the same time, a hard resin runner 4a communicating with the hard resin heating cylinder 3a and a soft resin runner 4b communicating with the soft resin heating cylinder 3b are formed.

On the other hand, the movable mold plate 2 is provided with a hard resin gate 5a and a soft resin gate 5b, as well as a protrusion bin 7a for protruding the runner part and a protrusion bin 7b for protruding the molded product.
When the mold is opened, only the runner part ejecting pin 7a is driven at the primary molding process position to eject the hard resin runner 4a' as shown in FIG. In the process, the runner part ejecting bin 7a and the molded product ejecting bin 7b are driven.

Then, from the hard resin heating cylinder 3a, polycarbonate 1-,
When a hard thermoplastic resin such as ABS is injected, the runner 4a
, flows into the cavity 6a through the gate 5a, and after cooling, when the fixed side mold plate 1 and the movable side mold plate 2 are opened, the runner part 4a'
is pushed out, and after rotating the movable mold plate 2 and clamping the fixed mold plate 1 and the movable mold plate 2, when soft resin is injected from the soft resin heating cylinder 3b, the runner 4b and the gate 5b and flows into the cavity 6b. Next, after cooling, when the fixed side template 1 and the movable side template 2 are opened, a soft resin molded in the secondary molding process is formed on the surface of the primary molded product 10a made of hard resin molded in the primary molding process. 2 made of resin
The molded product 10 integrally laminated with the next molded product 10b is ejected by the molded product ejection bin 7b, and the runner portion 4b' made of a soft resin material
protruded by a.

By the way, in such a molding process, since the runner part 4a' molded in the primary molding process is made of hard resin, the runner part 4a' is moved by the operation of the runner part ejecting bottle 7a.
' can be easily released from the mold, but since the runner part 4b' molded in the secondary molding process is made of soft resin, even if it protrudes, the runner part 4b' will stretch, making it impossible to release the molded product 10. There was a case.

[Object of the Invention] The present invention has been made to solve these problems, and involves injection molding a primary molded product using a hard resin, and then integrally injecting a soft resin into the primary molded product. To provide an injection molding method that allows a soft resin runner part to be easily cut from the molded product at a gate when a molded product having a two-layer structure of a hard resin layer and a soft resin layer is ejected using an ejector bottle. The purpose is to

[Summary of the Invention] The gist of the present invention is to inject a hard resin into a mold to form a primary molded product of the hard resin; A secondary molding process in which resin is injected through the runner and gate of the mold to integrally mold the hard resin molded part and the soft molded part, and after the secondary molding process, the molded product and the runner part are respectively molded. a mold release step in which the molded product is released by protruding it with an ejector bottle, and at the protruding position of the runner portion of the soft resin in the secondary molding step,
The injection molding method is characterized in that in the primary molding step, the hard resin injected into the mold remains.

[Embodiments of the Invention] The present invention will be described in detail below based on embodiments shown in the drawings.

FIG. 1 shows a mold for injection molding in which the method according to the present invention can be effectively carried out, and the same parts as those of the mold shown in FIG. 3 are given the same reference numerals, and the structural description thereof will be omitted.

In the mold of this embodiment, a runner 4a is formed on the movable mold plate 2 to guide the hard resin from the hard resin heating tube 3a to the gate 5a in the primary molding process, and when the movable mold plate 2 is rotated intermittently. , the runner 4a between the hard resins is formed at a position facing the runner 4b for the soft resin formed on the stationary template 1.

Furthermore, when the mold is opened, the ejector pin 7a for ejecting the runner and the ejector pin 7b for ejecting the molded product are both inactive at the primary molding process position, and are activated at the same time at the secondary molding process position. ing.

That is, thermoplastic resin such as polycarbonate injected into the mold from the hard resin heating tube 3a passes through the runner 4a and gate 5a formed on the movable mold plate 2 and into the primary molding cavity 6a. Injected. Next, after cooling, the fixed side template 1 and the movable side template 2 are opened, and the movable side template 2 is moved so that the primary molded product 10a made of hard resin and the runner part 4a' are moved to the secondary molding process side. is intermittently rotated at a predetermined angle about the center line °C, and the fixed side mold plate 1 and the movable side mold plate 2 are clamped.

Next, a soft resin such as urethane type elastomer is injected into the mold from the soft resin heating cylinder 3b, and the soft resin is poured into the runner 4b.
, flows into the cavity 6b through the gate 5b, and a soft resin runner part 4b' is formed on the surface of the hard resin runner part 4a'.
At the same time, a secondary molded product 10b made of a soft resin is fused to the surface of the primary molded product 10a made of a hard resin, thereby forming a molded product 10 having a two-layer structure of a hard layer and a soft layer. .

The molded product 10 can be released from the mold by opening the fixed mold plate 1 and the movable mold plate 2, as shown in FIG.
and 7b operate at the same time, and the ejector bottle 7a abuts against the hard resin runner portion 4a', and the ejector bottle 7b abuts against the molded product 10, and is respectively ejected in the mold opening direction.

At this time, since the soft resin runner part 4b' is integrally fused with the hard resin runner part 4a', it will hardly stretch even if a tensile force is applied, so that the gate 5b will not be stretched from the runner part 4b'. It is cut from the corner 11 extending inward by the gage 1-5b. Of course, at the same time, the hard resin runner portion 4a' is also cut at the gate 5a.

Therefore, when releasing the molded product 10, the elongation of the soft resin runner part 4b' molded in the secondary molding process is regulated by the hard resin runner part 4a' molded in the primary molding process. The molded product can be released from the mold with a predetermined operating stroke of the ejector bottles 7a, 7b.

In addition, in the above embodiment, the runner portion 4b' made of soft resin
is formed on the hard resin runner portion 4a', but a raised portion made of hard resin may be separately molded during the primary molding to correspond to the soft resin runner portion.

[Effects of the Invention] As explained above, according to the present invention, the runner portion of the soft resin is covered with the hard resin and protrudes, so there is no problem that the runner portion of the soft resin stretches and becomes impossible to cut. The effect is that the problem is eliminated and the molded product can be reliably released from the mold.

[Brief explanation of drawings]

FIGS. 1 and 2 show a mold in which the present invention can be effectively carried out, with FIG. 1 showing the mold in a closed state and FIG. 2 showing the mold in an open state. FIG. 3 shows a conventional injection mold, and FIG. 4 shows the mold in an open state. 1... Fixed side template 2... Movable side template 3a,
3b... Heating cylinder 4a, 4b... Runner 4a'
, 4b'...Runner parts 5a, 5b...Gates 6a, 6b...Cavity

Claims (1)

[Claims] A primary molding process in which hard resin is injected into a mold to form a primary molded product of hard resin, and a soft resin is injected into the primary molded product through the runner and gate of the mold to form a hard resin. It consists of a secondary molding process in which the molded part and the soft molded part are integrally molded, and a mold release process in which, after the secondary molding process, the molded product and the runner part are respectively projected with ejector pins and the molded product is released from the mold. An injection molding method, characterized in that the hard resin injected into the mold in the primary molding step remains at the protruding position of the runner portion of the soft resin in the secondary molding step.