JPS5818897B2 - Method for manufacturing a resin molded product having a hinge part - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a resin molded product having a hinge portion.

Conventionally, for example, as a resin molded product with a hinge part,
A vehicular lamp as shown in FIG. 1 may be arranged at the rear of an automobile and have a lamp body protruding into the trunk room.

That is, in this type of lamp, a lid body 2 for bulb replacement is connected to a main body part 1a of a lamp body 1 made of polypropylene resin via a hinge part 3 formed by providing a 7-shaped groove 31. The lid body 2 is constructed so that it can be opened and closed with respect to the main body portion 1a of the lamp body 1 by means of the hinge portion 3.

However, conventionally, the lamp body 1 is made of polypropylene resin, which is a tough material that is extremely difficult to break as a hinge. The mold must be made very thinly and with high precision compared to the basic wall thickness of the lamp body 1.
When molding, the resin does not wrap around well, so the molding pressure must be increased, but it is difficult to adjust the molding pressure,
In addition, since the 7-shaped groove 31 provided for forming the hinge part 3 is also required to be formed with high precision,
It has the disadvantage of requiring an expensive mold.

The object of the present invention has been made in view of the above-mentioned drawbacks.
1 for resin molded products that have a thin wall part in the hinge area
The entire surface layer is molded with polypropylene resin containing a 5 to 25 weight percent filler, and then cooled to concentrate the polypropylene resin on the surface side and confine the inorganic filler inside. By increasing the toughness and forming a bent part by bending the thin part and breaking the front side to the inside and leaving the back side, it has good formability.
Furthermore, the present invention provides a method for manufacturing a resin molded product having a hinge portion that does not require an expensive mold.

Hereinafter, the present invention will be explained in detail using embodiments shown in the drawings.

FIG. 2 is a perspective view showing an embodiment of a resin molded product formed by the manufacturing method according to the present invention, and in this embodiment, a lamp body is cited as the resin molded product.

That is, the lamp body 4 includes a main body 5 and a light bulb replacement lid that is connected to the main body 5 via a thin hinge 6 and can be opened and closed with respect to the main body 5. It is composed of 7 bodies, and the whole body is 15 to 25
It is integrally formed of polypropylene resin containing a weight-related inorganic optical filler, such as Merck.

This polypropylene resin mixed with talc is used to give the lamp body 4 its hardness and to make it easier to break, leaving a portion corresponding to the hinge portion 6 intact.

In addition, Yu Okibe said that if the content of Merck is 15 to 25% by weight, if more than 25% by weight of talc is mixed, the lamp body 4 itself will become too hard, and the entire body will break and break.
Furthermore, if the weight is less than 15%, there is a disadvantage that it will not be able to maintain its function as a lamp due to lack of hardness.

In view of these points, the content of talc is set at 15 to 25% by weight.

Note that reference numeral 51 indicates a bulb insertion hole, and a claw portion 71 provided on the lid body 7 is configured to engage with one end portion of a rim provided on the front side of the lamp body 4.

Next, to explain the method for molding the lamp body constructed as above, the polypropylene resin containing 15 to 25 weight parts of talc is heated and melted without being separated, and this material is molded into a mold using an injection molding machine. Light is emitted inside.

At this time, the V-shaped groove 61 forming the hinge portion 6 is also formed at the same time.

Note that the V-shaped groove 61 does not need to be formed with high precision, and in this embodiment, as shown in an enlarged view in FIG. 6
0 to 70%.

After molding the molded product, the molded product, that is, the lamp body 4
Since the surface side cools down faster than the inside, a thin film 41 of polypropylene resin is formed on the surface side of the lamp body 4 as shown in FIG. increases, and this center portion 42 becomes a tissue that is easily broken.

Therefore, if the lamp body 4 is then bent upward as shown in FIG. Only the polypropylene resin thin film 41 on the side opposite to the groove 61 remains unbroken.

As a result, the lamp body 4 will break at the hinge portion 6.

This thin film 41 made of polypropylene resin has toughness and will not break even with a small amount of force, and this thin film 41 constitutes a bent portion.

As explained above, according to the present invention, in a resin molded product having a thin wall portion in the portion corresponding to the hinge, the whole is molded with a polypropylene resin containing a filler of 15 to 25 weight percent of the unplaced part, and then cooled. By depositing polypropylene resin on the surface side and trapping the inorganic filler inside, most of the thin part is broken to form the bent part, so when molding, the thickness of the hinge part is basically the same. It is not necessary to make the wall thickness extremely thin, and therefore, there are no problems in molding as in the conventional method, and moldability can be improved.

In addition, even if a V-shaped groove is formed to provide a hinge part, this V-shaped groove does not need to be molded with high precision, so an ordinary mold can be used, and the cost is therefore lower than in the past. This has the effect that it is possible to measure the decrease in

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a vehicle lamp which is an example of a conventional resin molded product having a hinge portion, and FIG. 2 is an embodiment of a resin molded product having a hinge portion manufactured by the manufacturing method according to the present invention. Perspective views of example lamp bodies, Figures 3 to 5
The figure is an explanatory diagram showing the molding procedure. 4... Lamp body, 6... Scolding part, 6
2... Thin wall part.

Claims (1)

[Claims] 1. In a resin molded product having a thin wall portion in a portion corresponding to the hinge, the entire body is molded with a polypropylene resin containing a 15 to 25 weight factor filler in a non-placed area, and the inorganic filler is trapped inside by cooling. A method for manufacturing a resin molded product having a hinge portion, characterized in that a bent portion is formed by concentrating polypropylene resin on a surface side, bending the thin wall portion, and breaking the thin portion from the surface side to the inside.