JPH02155618A - Nut insert molding method - Google Patents

Abstract

PURPOSE:To certeinly insert a nut in a synthetic resin member at any angle and to facilitate the detachment of a molded body by setting a core assembly to the recessed part of a lower mold and filling the cavity of both registered molds with an uncured synthetic resin under pressure to surround the circumference of the nut and curing said resin to perform demolding. CONSTITUTION:A nut 2 is set to the surface of a core 1 and threaded with the bolt 3 protruding from the rear of the core 1 through a hole 13 to be fixed thereto and the head opening 21 of the nut 2 is sealed by a silicone cap 4. A core assembly M is set to the recessed part 51 of a lower mold 5 but the recessed part 51 is formed into an inverted trapezoidal cross-sectional shape and a semispherical recessed part 61 is formed to an upper mold 6 corresponding to the head of the nut 2. Then, the lower and upper molds 5, 6 are registered to perform the compression molding of an uncured resin W. The resin flows to the periphery of the nut 2 on both sides thereof and the resin stream from above is sent to the part easy to generate a short-circuit or welding behind the nut. After the resin is cured, a molded product 7 is removed along with the core assembly M and a protruding part 71 is ground by a grinder and the silicone cap 4 is detached.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a nut insert method for embedding and fixing a nut in a synthetic resin member.

(Prior Art and its Problems) In order to connect a synthetic resin member to another member, it may be necessary to attach a metal fitting, such as a nut, made of a material of the same type. For example, in recent years, as shown in FIGS. 5 and 6, it has been proposed to replaceably attach a roof R to which a rear window W is attached to an oven-type automobile body B. Body B to P
In order to fix the locking device M for attachment to the roof R, it is necessary to fix the nut N to the pillar inner part 2 of the roof R made of a synthetic resin member.

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 using adhesive A and rivets. 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 synthetic resin parts, it is desirable to adopt a nut insert method in which the nut is embedded and fixed at the same time as molding.However, in order to secure the nut in the mold cavity during molding, a depression or protrusion is formed on the mold surface, and the nut is inserted into it. If the nut is securely fixed, it is difficult to remove the product from the mold after molding.
If it is lightly engaged, it may come off during mold matching, get stuck between the molds, or cause defects in the product. Furthermore, the direction in which the screw holes are made is limited to the direction of mold removal due to the need to remove the mold after molding. Further, in recent years, there has been a trend toward automation of molding using robots, but the method of engaging and mounting a large number of nuts one by one has the disadvantage that it is not compatible with automation by robots.

(Problems to be solved by the invention) The present invention is not limited to the direction in which the mold is removed, but the nut can be reliably inserted into the synthetic resin member at any angle, and the nut can be easily removed. The objective is to provide a molding method that is easy to automate.

(Means for Solving the Problems) The present invention can solve the above problems by preparing a mold having a cavity into which a nest can be loaded into a nut insert, and by using a nest assembly in which a nut is temporarily fixed to the nest with a bolt. This method was developed with a focus on solving this problem.In order to embed and fix the nut at the same time as molding the synthetic resin part, the nest assembly, which is made by bolting the nut from the back side to the surface of the nest, is set in the recess of the lower mold. The upper mold is matched to the lower mold, and an uncured synthetic resin is pressurized and filled between the two molds to surround the nut, and after hardening, the mold is released and the bolt tightening is released, and the molded resin member and the nest are separated. The present invention provides a method for molding a nut insert into a synthetic resin member, the gist of which is a step of separating.

To apply this method to the hard top roof of an automobile, S
Although the MC (sort mold compound) method is employed, various pressure molding methods for synthetic resin products such as BMC (bulk mold compound) method and injection molding method may be employed.

The nest used in the present invention means a member that holds the nut in a predetermined position in the mold cavity, that is, the mold cavity.Since the nut is placed on the surface side of the nest, the predetermined storage recess can be adjusted according to the number of nuts installed. It is formed to correspond to the nut mounting position. The storage recess is preferably formed in the shape of an inverted truncated cone so that the flow of material around the nut is not inhibited during mold matching.

On the other hand, a bolt mounting recess for temporarily fixing a nut is formed on the back surface of the nest in correspondence with the storage recess, and a bolt insertion hole passes through the front and back recesses.

The nest used in the present invention can include not only single nuts arranged at intervals, but also connected integrated nuts.

In the present invention, the form of temporarily fixing the nut to the nest by tightening bolts includes a form in which the nut does not protrude outside the nut on the surface of the nest, but is inserted into the nut hole to securely fix the nut, and the nut is screwed onto the nut. Can be used in place of bolts in the form of ease of fixation and removal,
For reliability, it is preferable to use a bolt that can be screwed into a nut.

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

(Example) Fig. 1 is a process diagram of a nut insert molding method when the present invention is applied to molding a back pillar inner using the SMC method. The head opening 21 of the nut 2 is closed with a silicone cap 4.

In order to fix the nut 2 on the surface side of the nest 1, a predetermined inverted truncated conical storage recess 11 is formed corresponding to the nut mounting position according to the number of NANDs to be mounted. On the other hand, a mounting recess 12 for the bolt 3 for temporarily tightening the nut is formed on the back surface of the nest 1 corresponding to the storage recess 11, and the front and back recesses 11
, 12 are penetrated by bolt insertion holes 13. The nest used in the present invention can incorporate not only single nuts disposed at intervals, but also integrated joint nuts.As shown in FIG. 2, the nut 2 has an internal thread. A pair of outer peripheries i? where the robot claw engages with the center part of the screwed cylindrical body 20? i! 23. Circumferential flanz 22 sandwiched by 23
In addition to improving heat transfer by forming a hole, the change in resin capacity with the basic thick part is suppressed as much as possible, and the nut insert prevents the molding cycle from becoming longer around the nand. It is designed to prevent rotation after inserting.

(b) The nest assembly M is set in the recess 51 of the lower mold 5, or in order to ensure that the nest assembly M is attached, the recess 51 is connected to the slope 52, 52 along the periphery of the nest 1 and the The bottom portion and the abutting bottom surface 53 are formed into an inverted trapezoidal cross section. On the other hand, the upper die 6 is formed with four hemispherical parts 61 that correspond to the head of the nut 2 fixed to the surface of the nest 1 and are slightly larger than the outer diameter of the nut.

(c) Therefore, when the lower mold 5 and the upper mold 6 are matched and the uncured resin W is compression molded, the resin should flow smoothly from both sides around the nut 2 (see Fig. 3 (a)). )
, the resin flows from above through the upper mold recess 61 of the nut head to the part behind the nut where welds or welds are likely to occur (see FIG. 3(b)). Therefore, the nut insert part is larger than the product wall thickness, but since the central flanone 22 protrudes (see Figure 4), in order to improve heat transfer to the surrounding area, the resin capacity with the basic wall thickness is reduced. Since the change in is suppressed as much as possible, the molding cycle near the periphery of the nut is prevented from becoming longer.

(d) After the resin has hardened, the molded product 7 is demolded together with the nest assembly M. (e) While removing the temporary fixing bolt 3 and removing the nest I, the protrusion 71 protruding from the nut insert part is removed using a grinder or the like. Grind.

('') Then, leave the silicone cap 4 as it is and apply coating C. (g) Remove the silicone cap 4 from the head of the nut 2,
Complete the nut insert molding.

(Effects of the Invention) As is clear from the above description, according to the present invention, when embedding and fixing a nut at the same time as molding a synthetic resin member, a nest assembly in which a nut is fixed in advance using a nest is inserted into a nut. Since the nut is set in the insert part, it is easier to attach and remove the nut compared to the nut attachment method in which four parts or convex parts are provided on the mold surface. In addition, since the installation of the nut into the mold is completed by installing the nest assembly into the lower mold, automation of nut insert molding using a robot is easy. Furthermore, since the screw hole direction of the nut is not limited to the die cutting direction, there is an advantage that insert molding of the nut can be widely used.

[Brief explanation of the drawing]

Figures 1 (a) to (g) are process diagrams of a nut insert molding method when the present invention is applied to molding a back pillar inner by the SMC method, and Figure 2 (aXb) is a diagram of a nut inserted by the method of the present invention. FIG. 3 (aXb) is a plan view and side view showing the resin flow in the molding method of the present invention, FIG. 4 is a cross-sectional view showing the state of compression molding of the nut insert portion, and FIG. 5 6 is a schematic side view of a specific example requiring insert molding, FIG. 6 is a sectional view taken along the line VT-Vl, and FIG. 7 is a structural diagram showing a conventional nut fixing method. l...Nest, 2...Nut, 3...Temporary bolt, 4
・Noricon cap, 5...lower mold, 6 upper mold.

Claims (1)

[Claims] 1. When embedding and fixing a nut at the same time as molding a synthetic resin member, a nest assembly formed by tightening bolts from the back side of the nut to the surface of the nest is set in a lower mold recess, and the lower mold In contrast, the process of pressurizing and filling uncured synthetic resin between the two molds where the upper mold is matched to surround the nut, releasing the mold after hardening, releasing the bolt tightening mentioned above, and separating the molded resin member and the nest. A nut insert forming method characterized by comprising the steps of: