JPS6176333A - Jointing method among molded articles by injection molding - Google Patents

Abstract

PURPOSE:To enable to unify reliably two molded articles at the time of injection molding, by providing a first core opening and closing a communication part and a second core whose tip provided with a stepped part is brought into contact with the first core are provided on one side of two cavities provided by making them communicate with each other. CONSTITUTION:Two cavities having resin pouring inlets respectively are provided within the same mold by making the cavities communicate with each other, and an advancable and retreatable first core 9 opening and closing a communication part 6 and an advancable and retreatable second core 10 whose tip provided with a stepped part 10a is brought into contact with the first core 9 are provided on the communication part 6 of the one side cavity 4. The first core 9 and second core 10 are made to abut against each other by making them move forward and the communication part 6 is closed by the first core 9. Then after a molded material 11 has been molded by injecting resin to the cavity 4, both the cores are moved backward up to a mold surface. Then when the other resin is injected successively to the other cavity 5, a spacial part 12 is filled with a part of the resin by flowing the resin into the spacial part 12 through the communication part 6 and a joint part 15 which is unified with the molded material 11 is generated through an undercut 14 formed by the stepped part 10a.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a method for joining molded bodies together by injection molding, in which two molded bodies injection molded in the same mold are joined together at the same time as molding. It is.

(Prior Art) Generally, two molded bodies are joined during injection molding using resin fusion. In addition, if the two molded objects are made of different resins and it is difficult to fuse them together, or if there is a risk that the joint will be damaged later due to the difference in shrinkage rate, use adhesives, screws, or insets after molding. The connection is performed using methods such as

(Problem to be solved by the invention) For this reason, when molding two molded bodies using resins of different materials, it is necessary to select materials that have approximately the same shrinkage rate and are easy to fuse, so the resin used must be There was a problem in that it was limited.

Furthermore, when bonding is performed after molding, the number of steps increases accordingly, which results in longer production times and losses, resulting in higher costs.

(Means for Solving the Problems) This invention has been devised to solve the above-mentioned conventional problems, and its purpose is to achieve two
We have developed a method for joining molded bodies that can reliably integrate two molded bodies during injection molding, and that will not damage the bonded parts due to the difference in shrinkage rate even if the resins used have different shrinkage rates. It is about providing.

According to the present invention, two cavities each having a resin injection port are provided in the same mold so as to communicate with each other, and one of the cavities is provided with a first core of a required size that also serves as an opening/closing member for the communication portion. , a second core is provided at a position opposite to the first core and whose stepped tip is in contact with the first core, and is movable back and forth, and these two cores and the stepped portion allow injection to be carried out in one cavity. A joint part formed by forming a space connected to the communication part in the molded body, filling the space with a part of the molded body injection-molded by the other cavity, and integrating the molded body by an undercut. It forms.

(Function) In the above method, a first core and a second core provided in one cavity are brought into contact with each other, resin is injected into the cavity to form one molded body, and then the core is retreated to the mold surface. When moved, a space is created in the molded body that communicates with the other cavity, and an undercut is formed in the space by the stepped portion of the second core.

After the core is moved backward, the resin injected into the other cavity flows into the space from the communication part, and a joint is formed therein which is prevented from separating by the undercut.

This will be explained in detail using an illustrated example. Note that the same parts are indicated by the same symbols.

(Example) Example 1 (Figures 1 to 3) First, to explain the structure of the mold, two cavities 4 and 5 are provided between the fixed mold 2 and the movable mold 3 of the same mold 1. Both cavities 4 and 50 are provided close to each other, and communication portions 6 are formed through gaps at required locations, and each cavity 4 and 5 is provided with an injection port for the resin passages 7 and 8 provided in the fixed mold 2. This allows resin to be injected into each cavity.

Furthermore, in a portion of one cavity 4 adjacent to the communication section 6, there is a first core 9 that can move forward and backward on the fixed platen 2 side that opens and closes the communication section 6, and a step that is located opposite the first core 90. A second core 1° is provided on the side of the movable platen 3, the tip of which is provided with the portion 10a, in contact with the first core 9, and is movable forward and backward.

Injection molding using the above mold is performed by first moving the first core 9 and the second core 10 forward to abut each other, as shown in FIG. Close.

Next, after resin is injected into the cavity 4 to form a molded body 11, when both cores are moved backward to the mold surface, a space 12 is created in the molded body from the communication portion 6, as shown in FIG.

Then, when another resin is subsequently injected into the other cavity 5, a part of the resin flows into the space 12 from the communication part 6 and is filled, and at the same time the molded body 13 is molded in the cavity 5. , the undercut 14 formed by the step 10a creates a joint 15 that is integrated with the molded body 11.

Due to this joining part 15, the molded bodies 11 and 13 are joined together as shown in FIG. 4, regardless of whether they are made of the same or different materials, and the integration will not be impaired unless the joining part 15 is destroyed. .

Embodiment 2 (FIGS. 5 and 6) This embodiment is based on the main body part 2 of the watch shown in FIGS. 7 and 8.
1 and the belt part 22 are integrally combined during injection molding, and in this case, the cavities 5, 5 forming the belt part n are placed adjacent to each other on both sides of the above-mentioned one cavity 40 in which the main body part 21 is molded. A pair of first cores 9, 9 for opening and closing both communicating portions 6, 6, respectively, are installed in the cavity 4, and a pair of second cores 10, to which a stepped portion 10a forming an undercut 14 is provided at the tip. are provided in combination in the same manner as in the first embodiment.

In the injection molding, the main body part 21 is first molded with the resin 7 injected into the cavity 4, and then the first core 9 and the second core 10 are molded.
After moving backward, resin 8 is injected into the cavity 5 to form the belt part n. A part of the resin forming the belt part A flows into the main body part 21 from which the communicating parts 6 and 6 have the undercuts 14 protrudingly formed, as in the first embodiment, and forms the joint part 15 there. It is integrated with the main body part 21.

(Effects of the Invention) As described above, the present invention includes a first core that opens and closes the communication portion in one of the two cavities that are provided in communication with each other, and a step that is located opposite to the first core. The tip with the part is the first
A second core that is in contact with the core is provided, and the movement of these two cores forms a space in the previously injection-molded molded product into which a part of the molded product that is later injection-molded is filled. The undercut formed in a protruding manner forms a joint where one molded body and a part of the other molded body are integrated, and this connects the molded bodies to each other. Even if the resin materials used are different, the image molded bodies can be reliably bonded.

Furthermore, the bonded portion is prevented from separating by the undercut, so it is robust, and even if there is a difference in yield, the bonded portion will not be damaged. Moreover, since bonding occurs at the same time as injection molding of the molded bodies, post-processing for bonding is not required, and costs can be reduced. Furthermore, unlike the case of fusion bonding, there are many advantages such as there are no restrictions on the resin used (and the resin can be freely selected depending on the purpose of the molded article).

[Brief explanation of the drawing]

The drawings show an embodiment of the method of joining molded bodies together by injection molding according to the present invention, and FIGS. 1 to 3 are schematic vertical cross-sectional views of a mold sequentially showing the molding process of the first embodiment, FIG. 4 is a vertical cross-sectional view of the bonding portion between molded bodies, FIGS. 5 and 6 are schematic vertical cross-sectional views of a mold sequentially showing the molding process of the second embodiment, and FIG. 7 is a longitudinal cross-sectional view of the molding process of the second embodiment. FIG. 8 is a plan view of the molded product formed by the method, and FIG. 8 is a longitudinal sectional view thereof. 5.4...Cavity 6...Communication section 9...First core 10...Second core 10a...Step part 11, 1
3...Molded body 12...Space part
14... Undercut 15... Joining part 21... Watch body mark 22...
・・・Band club

Claims (1)

[Claims] Two cavities, each having a resin injection port, are provided in the same mold so as to communicate with each other, and one of the cavities has a first core of a required size that also serves as an opening/closing member for the communication portion, and the first core
A second core is provided at a position opposite to the core and whose tip with a stepped portion contacts the first core, and is movable back and forth, and injection molding is performed in one cavity using these two cores and the stepped portion. A space connected to the communication part is formed in the body, and a part of the molded body injection molded by the other cavity is filled in the space to form an integrated joint by an undercut. A method for joining molded bodies together by injection molding, characterized in that: