JPH02155619A - Mold structure for pressure molding of synthetic resin - Google Patents

Abstract

PURPOSE:To easily remove an inert part and to prevent the generation of a defect due to a short-circuit or welding by molding a cavity permitting the flow of resin between the top part of the insert part subjected to insert molding and the surface of a mold. CONSTITUTION:A nut 2 is set to the surface of a core 1 and threaded with a bolt 3 to be fixed thereto and the head opening 21 of the nut 2 is sealed with a silicone cap 4. A circumferential flange 22 is formed to the central part of a cylinder main body 21 provided with an inner screw of the nut 2 to enhance the transfer of heat and suppresses the volumetric change of the resin of the thick wall part of a base body as low as possible and it is prevented that the molding cycle in the vicinity of the circumference of the nut becomes long by the insertion of the nut while a part of the flange is notched to prevent the rotation of the nut after insertion. A semispherical recessed part 61 having an outer diameter slightly larger than that of the nut is formed to an upper mold 6 corresponding to the head of the nut 2. When lower and upper molds 5, 6 are registered to perform the compression molding of uncured resin W, a resin stream from above is guided to the part easy to generate a short-circuit or welding behind the nut 2 through the recessed part 61 of the upper mold 6.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a synthetic resin pressure molding mold structure for embedding and fixing an insert part such as a nut into a synthetic resin member.

(Prior Art and its Problems) In order to join a synthetic resin member to another member, it may be necessary to embed a metal fitting made of a different material, such as a nand, in some cases. For example, in recent years, as shown in FIGS. 5 and 6, a rear window W has been installed on an oven-type automobile body B.
It has been proposed that the hard top roof R to which the hard top roof R is attached is replaceably mounted, and in order to fix the locking device M for attachment to the body B to the back pillar P of the hard top roof R, the hard top roof R is made of a synthetic resin member. R
It is necessary to fix the nut N to the pillar inner I.

Conventionally, in order to fix a nut to a synthetic resin member, as shown in Fig. 7, bolt holes H are drilled in the synthetic resin member P in post-processing, and a reinforcing iron plate F with nuts attached is attached to the back side of the synthetic resin member P.
was attached with adhesive A and rivet L. However, the post-work installation has disadvantages in that it has poor workability, impairs the appearance of the mounting portion, and has poor mounting accuracy.

Therefore, when molding a synthetic resin member, it is desirable to adopt a nut insert method in which a nut is embedded and fixed at the same time as molding, but if there is an insert part such as a nut, careful attention must be paid to the flow of resin around it. In other words,
If the resin fluidity is too good, the molten resin will flow into the threaded parts, making it difficult to remove it after hardening. On the other hand, if the resin fluidity is low, shorts and weld defects are likely to occur downstream of the insert part (see Figure 4).

(Problem of the Invention) An object of the present invention is to provide a mold structure suitable for embedding and molding an insert part in conventional resin pressure molding.

(Means for Solving the Problems) The present invention has been made with the focus on the fact that the drawbacks in molding of insert parts can be solved by controlling the flow direction of the resin toward the downstream side of the insert parts. A mold structure for pressure molding that pressurizes and fills a material into a mold to form a product, at a position facing the top of the insert part on the mold surface that molds the front side of the product into which the insert part is embedded. , a mold structure for pressure molding of a synthetic resin, characterized in that a recess is formed between the top of the insert part and the mold surface to allow resin to flow during mold matching.

In particular, when the insert part is a nut, in order to avoid the height of the nut almost matching the product surface line, a nut storage recess is provided in the lower mold, while a predetermined gap for resin flow is provided between the upper mold and the top of the nut. This results in the formation of a depression that forms πa.

According to the present invention, even if the resin fluidity is low, as shown in FIG. 3, the part that passes through the top of the insert part and is downstream of the insert part, as shown in FIG. Resin flow is induced, and as a result, defects such as short circuits do not occur.

For the wooden structure, the SMC (Sheet Mold Compound) method or a structure that can be applied is used for the hard top roof of an automobile, but the BMC (Bulk Mold Compound) method and the injection molding method can be used for synthetic resin products. It may be employed in various pressure molding molds.

The parts to be inserted in the present invention may be fixed to the lower mold through a concave or convex part provided in the recess of the lower mold, but they can also be fixed to a predetermined surface side through a nest that holds a nut in a predetermined location. It is also possible to arrange nuts.

Hereinafter, the present invention will be described in detail based on specific examples shown in the accompanying drawings.

(Example) Fig. 1 is a cross-sectional view of the mold structure when the present invention is applied to molding a back pillar inner using the SMC method. It is screwed onto the protruding bolt 3 and fixed, and the head opening 21 of the nut 2 is closed with the silicone cap 4.

As shown in FIG. 2, the nut 2 has a circumferential flange 22 formed in the center of a cylindrical body 21 with an internal thread to improve heat transfer and change the resin capacity with the basic thick part. While the nut insert prevents the molding cycle near the nut from becoming too long, a portion of the nut insert is cut out to prevent rotation after the insert is inserted.

The nest assembly M is set in the recess 51 of the lower mold 5, and the recess 51 is formed to have an inverted trapezoidal cross section in order to securely attach the nest assembly M.

On the other hand, the upper die 6 has a nut 2 fixed to the surface of the nest 1.
A hemispherical recess 61 slightly larger than the outer diameter of the nut is formed corresponding to the head of the nut. Specifically, as shown in Fig. 2, a recess with an outer diameter of 12 mm is formed for a nut with an outer diameter of 10 mm during mold matching, and a gap of 0.5 to 0.5 mm is formed between the top of the nut and the recess.
It is appropriate to form a gap of 1.0 mm.

Therefore, when the lower mold 5 and the upper mold 6 are matched and the uncured resin W is compression molded, the resin flows smoothly from both sides around the nut 2, and the upper mold recess 61 of the nut head
The resin flows from above to the joint behind the nut or to the part where welds are likely to occur (see Fig. 3).

Moreover, although the nut insert part is larger than the product wall thickness, the central flange 22 protrudes, which improves heat transfer to the surrounding area and minimizes changes in the resin volume from the basic thick part. This prevents the molding cycle near the periphery from becoming longer (see FIG. 2).

(b) After the resin hardens, the molded product 7 is demolded together with the insert preassembly M, the temporary fixing bolts 3 are removed, and the insert l is removed.
Nut relief convex portion 7 protruding from the nut insert part
1 is ground with a grinder or the like, and then the silicone cap 4 is removed so that a bolt can be screwed into the mounting nut 2.

(Effects of the Invention) As is clear from the above explanation, according to the present invention, when embedding and fixing an insert part such as a nut at the same time as molding a synthetic resin member, the front side of the product in which the insert part is embedded is molded. A depression was formed on the mold surface facing the top of the insert component to ensure resin flow between the neck of the insert component and the mold surface during mold matching, thereby preventing the occurrence of welds and welds downstream of the insert component. As a result of the resin flowing from above into the easily damaged parts, defects such as short circuits do not appear at least on the surface of the product, and the insert molded product can be molded with an excellent appearance. Furthermore, since the recessed portion is formed in a portion where the insert part is flush with the product surface and is likely to interfere with the upper mold, there is no chance of interference with the upper mold and damage to the mold during mold clamping. Furthermore, since the nut release portion protrudes from the product surface, even if the insert part is buried in the resin, it serves as a mark and has the advantage of facilitating screw hole extraction during finishing.

[Brief explanation of the drawing]

Figures 1 (a) and (b) are a cross-sectional view of a ten-groove insert molding die when the present invention is applied to molding a back pillar inner using the SMC method, and a cross-sectional view during demolding, and Figure 2 is a cross-sectional view of the mold according to the present invention. FIG. 3 is an explanatory diagram showing the state of resin flow in the mold of the present invention, FIG. 4 is an explanatory diagram showing the state of resin flow in conventional insert molding, and FIG. 5 is an explanatory diagram showing the state of resin flow in conventional insert molding. FIG. 6 is a schematic side view of a specific example that requires this, FIG. 6 is a cross-sectional view taken along line II-VI, and FIG. 7 is a structural diagram showing a conventional nut fixing method. 2...Nut, 5...Lower mold, 51...-do type recess 6...''2 mold, 61...Upper mold recess. Figure 1

Claims (1)

[Claims] 1. A pressure molding mold structure for molding a product by pressurizing and filling a synthetic resin material into the mold, the mold surface molding the front side of the product in which an insert part is embedded and molded. A mold structure for pressure molding of a synthetic resin, characterized in that a depression is formed at a position facing the top of the insert part to allow resin flow between the top of the insert part and the mold surface during mold matching. . 2. The insert part is a nut, and the lower mold is provided with a nut storage recess that makes the height of the nut approximately match the product surface line, while a predetermined resin flow gap is formed between the upper mold and the top of the nut. 2. The mold structure according to item 1 above, which is formed by forming a depression.