JPH0444886B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) This invention provides a method for embedding a male-threaded insert by installing a male-threaded insert in a cavity and injecting a reactive liquid raw material into the cavity. The present invention relates to a method of manufacturing a plastic molded article.

(Prior Art) Automotive parts such as spoilers, instrumentation panels, and other plastic molded products often have male screws embedded and fixed therein in order to attach the plastic molded product to an automobile or the like.

The production of such a plastic molded product in which a male screw is embedded and fixed is normally carried out as follows. First, as shown in FIG. 6, the male threaded insert 14, in which the male thread 12 is fixed to the insert 10 by welding or the like, is placed on the cavity surface 1 of the mold 16.
The male screw 12 is inserted into the hole 20 provided at 8 to fix the device in a predetermined position. Next, as shown in FIG. 7, a reactive liquid raw material, such as a urethane raw material, is injected into the cavity 24 of the mold 16, 22 in which the male threaded insert 14 is installed, and the plastic molded product in which the insert 10 is embedded is injected. It is manufactured. Note that the arrow A direction is the mold opening direction.

However, since the male thread 12 is threaded spirally from one end to the other end of the outer circumferential surface, no matter how much the alignment between the outer circumferential surface of the male thread 12 and the inner circumferential surface of the hole 20 is improved, the cavity 24 The reactive liquid raw material injected into the inside enters into the thread of the male screw 12.

Therefore, it is necessary to remove the resin that has solidified within the threads after molding the product. Furthermore, since it is difficult to completely remove the dirt, there is a risk that the nut may not be fully tightened when the product is installed. Furthermore, the product is molded into a mold 16.
There is also a risk that the screw threads may be soaked or the cavity surface may be damaged when taking it out or removing the resin.

(Problems to be Solved by the Invention) This invention solves a problem that conventional manufacturing methods have, namely, when manufacturing a plastic molded product having a male threaded insert, the threads of the male thread become clogged with resin. This is intended to solve the various problems mentioned above.

(Means for Solving the Problems) The present invention provides a plastic molding method in which a male-threaded insert is installed in a cavity, and a reactive liquid raw material is injected into the cavity to embed the insert in a molded product. In the method for manufacturing a molded product, the male threaded portion of the insert is tightly wrapped in advance with a cylindrical elastic body, and
The male screw portion enclosed by the cylindrical elastic body is press-fitted into a predetermined recess formed on the cavity surface to fix the insert in position, and then a reactive liquid raw material is injected to perform integral molding. It is characterized by this.

(Function) In this invention, the male threaded portion of the insert is tightly wrapped in advance with a cylindrical elastic body, and the male threaded portion wrapped by the cylindrical elastic body is placed in a predetermined recess on the cavity surface. Since the male threaded insert is installed in the cavity by press-fitting, the elastic body comes into close contact with the outer circumferential surface of the male thread, and the outer circumferential surface of the male thread is completely sealed by the elastic body. Therefore, the reactive liquid raw material injected into the cavity cannot enter between the outer circumferential surface of the male thread and the inner circumferential surface of the elastic body, and a plastic molded product in the shape of a cavity is formed without clogging the threads. And the plastic molded product is
A male threaded insert is embedded and fixed, and a series of manufacturing operations is completed by removing the elastic body from the male thread after demolding. This eliminates the need for the conventional work of removing resin stuck in the screw threads, and
This solves the various problems mentioned above caused by resin clogging the screw threads.

(Example) The present invention will be described below based on an example and with reference to the drawings.

FIG. 1 shows one embodiment of this invention.
FIG. 3 is a cross-sectional view showing a case where a cylindrical elastic body 32 is tightly wrapped around a male thread 30 and the elastic body 32 is inserted into a hole 38 provided in a cavity surface 36 of a mold 34.

It is preferable that the male thread has no threads over a predetermined length of the neck, such as the male thread 31 shown in FIG. 3, than the thread 30 shown in FIG. 1, which has threads up to the neck. This is because if the neck does not have a thread over a predetermined length, the elastic body 32 can be completely tightly attached to the outer circumferential surface of the neck due to its elasticity during wrapping, and the sealing performance of the neck can be further improved.

Note that the male thread 30 is fixed to the metal insert 40 by welding or the like to form a male threaded insert 42.
used as. The metal insert 40 is designed to suit the purpose, shape, etc. of the plastic molded product, and has the function of fixing the male screw 30 within the molded product, as well as maintaining the shape and increasing the rigidity of the molded product. It is.

The cylindrical elastic body 32 is made of an elastic body such as rubber, and has a hole 44 that allows it to tightly fit around the male screw 30. The elastic body 32 may have a round or square tube shape as shown in FIG. The outer diameter of the male screw 30 is smaller than that of the male screw 30, so that when wrapped, the elastic body 32 tightens the neck of the male screw 30 and comes into close contact with the neck, so that this part can be completely sealed by the elastic body 32. is preferred. In this case, if the male thread is threaded to the neck, the thread will bite into the elastic body 32.

The mold 34 is a split mold, and has a cavity surface 36 provided with a hole 38 into which the cylindrical elastic body 32 can be inserted. Further, the hole 38 may be replaced by a groove shape. This hole 38 or groove has a slightly smaller dimension than the outer shape of the cylindrical elastic body 32, so that when the elastic body 32 is fitted into the hole 38 etc., the elastic body 32 is removed from the outer shape by the inner surface of the hole 38 etc. It is preferable to tighten the screw so that it is in close contact with the outer circumferential surface of the male thread. Further, as shown in FIG.
2 may be inserted, and the elastic body 32 may be sandwiched between the other split mold 50. In addition, in the split molds 46 and 50 shown in FIG. 4, the male screw 31 is provided upright in a direction different from the mold opening direction. Furthermore, regarding the split molds 52 and 54 shown in FIG.
The male screw 31 is erected in a direction different from the mold opening direction. 33 is a cylindrical elastic body, and 39 is a hole provided in the cavity surface.

Male threaded insert 42 made in this way
A cylindrical elastic body 32 is tightly wrapped around a male screw 30 of the cylindrical body.
At the time of wrapping, the elastic body 32 expands slightly, and the resulting elastic restoring force brings the mouth of the elastic body 32 into close contact with the neck of the male screw 30. As a result, the neck of the male screw 30 is completely sealed by the elastic body 32.

This cylindrical elastic body 32 is press-fitted into a hole 38 provided in a cavity surface 36 of a mold as shown in a chain line as shown in FIG. As a result, the elastic body 32 is tightened from the outside by the inner surface of the hole, and is further brought into close contact with the outer periphery of the male screw 30. In addition, the split molds 46, 5 in Fig. 4
Similarly, when the elastic body 32 is clamped with the male screw 3
Closely adheres to the outer peripheral surface of 1.

Next, a reactive liquid raw material such as a urethane raw material is injected into the mold cavity (corresponding to 24 in FIG. 7). The injected reactive liquid raw material is
Since the neck of the screw 0 is sealed by the cylindrical elastic body 32, it does not enter between the outer circumferential surface of the male screw 30 and the inner surface of the elastic body, and the molded plastic product in a cavity shape is obtained without clogging the screw thread.

The resulting plastic molded product has the insert 40 portion of the male threaded insert 42 embedded and fixed within the molded product. After demolding the molded product, the cylindrical elastic body 32 is removed from the male thread 30, resulting in a plastic molded product having a desired male threaded insert. The removed cylindrical elastic body is used repeatedly in manufacturing the plastic molded product.

(Effects of the Invention) The present invention includes tightly wrapping the male threaded portion of the male threaded insert with a cylindrical elastic body,
The male threaded part enclosed by the cylindrical elastic body is press-fitted into a predetermined recess on the cavity surface, and a reactive liquid raw material is injected into the cavity to produce a plastic molded product. We were able to obtain similar effects.

In other words, the screw threads of the male screws can be prevented from being clogged with resin, thereby eliminating the need to remove the resin (burrs) and preventing the screw threads from collapsing, which tend to occur when demolding the product or removing burrs. This made it possible to prevent scratches on the mold surface.

In addition, even in high-pressure injection molding such as polyurethane RIM molding where liquid raw materials can easily enter even the smallest gaps, male threaded inserts can be embedded and fixed within the molded product without clogging the threads with resin. It was summer.

Moreover, even if the male thread is erected in a direction different from the opening direction of the mold, the product can be molded without any problem.

Furthermore, since the cylindrical elastic body can be used repeatedly,
The use of the elastic body does not lead to an increase in costs.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention in which a male threaded portion is tightly wrapped by a cylindrical elastic body, and the male threaded portion wrapped by the cylindrical elastic body is placed in a predetermined recess on the cavity surface. 2A and 2B are plan views of the cylindrical elastic body, FIG. 3 is a sectional view illustrating a male threaded insert in another example of the present invention, and FIGS. FIG. 5 is a cross-sectional view showing still another example of the present invention, FIG. 6 is a cross-sectional view showing a conventional male threaded insert when the cavity surface is installed, and FIG. 7 is a cross-sectional view showing the conventional manufacturing process. be. 30... Male screw, 32... Cylindrical elastic body, 36... Cavity surface, 38... Hole, 40... Insert, 42...
Male threaded insert, 44 holes.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a plastic molded product, in which a male threaded insert is installed in a cavity and the insert is embedded in the molded product by injecting a reactive liquid raw material, comprising: The insert is tightly wrapped in advance with a cylindrical elastic body, and the male threaded part wrapped with the cylindrical elastic body is press-fitted into a predetermined recess formed on the cavity surface. A method for manufacturing a plastic molded article having a male threaded insert, characterized by fixing the position and then injecting a reactive liquid raw material to perform integral molding. 2. A method for manufacturing a plastic molded product having a male threaded insert as set forth in claim 1, wherein the male thread insertion opening of the cylindrical elastic body is smaller than the male thread diameter. 3. A method for manufacturing a plastic molded product having a male threaded insert as set forth in claim 1 or 2, wherein the neck of the male thread does not have a predetermined length thread. 4. A method for manufacturing a plastic molded product having a male threaded insert according to any one of claims 1 to 3, which comprises sandwiching a cylindrical elastic body wrapped with a male thread between split molds.