JP3093392B2 - Plastic molding equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for molding a plastic molded article which requires rigidity at a portion to be attached to an object to be attached, for example, a mudguard for an automobile.

[0002]

2. Description of the Related Art If a mudguard for an automobile is taken as an example of a plastic sandwich molded product requiring rigidity in a portion to be mounted on a body to be mounted, a conventional mudguard 20 has a body 21 and a body 21 as shown in FIG. And sheet metal inserts 22 and 23 inserted.

[0003]

However, the conventional mudguard 20 has the following disadvantages. (A) The use of a sheet metal insert increases the weight of the mudguard and increases the wall thickness. (B) Since molding is performed manually, the molding cycle is reduced. (C) Since the sheet metal insert is set in the main body, there is a possibility that the sheet metal insert will be damaged by the mold if it is erroneously operated. (D) Pin marks for holding the sheet metal insert remain on the molded product. (E) Due to the presence of the sheet metal insert, the flow of the resin injected into the mold is changed, and a weld is generated to deteriorate the appearance.

An object of the present invention is to provide an apparatus for molding a plastic molded article which does not have the above-mentioned disadvantages. As a prior art document of the present application, there is JP-A-1-233178. In the present invention, a soft material is injected into a mold and then a hard material is injected to reinforce a bolt mounting hole. However, there is a fear that the hard material may be injected more than necessary. For example, in the case of a mat guard for an automobile, the hard material may enter the flap portion where the soft material is required and have an unnecessarily high rigidity.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method of fixing a fixed mold in a cavity of a molding die for a plastic molded product corresponding to a bolt mounting hole of the plastic molded product. In addition, the movable mold is provided with circular projections facing each other, a slit is formed between the ends of the circular projections, and a resin press-fitting passage is provided in the slit of one of the projections.

[0006]

First, a soft material is injected into a cavity from a resin press-in path through a slit, and then a hard material is injected into the cavity. At this time, the slit has a thin circular plate-like function of a gate for injecting resin radially. Therefore, the rigidity of the molded article is increased around the circular protrusion due to the presence of the hard material. When the plastic molded product is taken out of the mold, two circular holes defined by a thin film of a soft material and a film of a hard material are formed in the molded product so as to face each other. When the thin film is removed, the two circular holes communicate with each other to form a bolt mounting hole, and the periphery thereof has high rigidity as described above.

Here, the soft material means a synthetic resin having relatively high flexibility.
, A soft PVC resin, an EVA (ethylene / vinyl acetate) resin, an SEBS (styrene / ethylene / butadiene styrene) resin, an SBS (styrene / butadiene / styrene) resin, and the like.
The hard material means a hard synthetic resin having relatively large rigidity, such as an AS resin, an ABS resin, and a hard PVC.
Examples thereof include a resin and a polypropylene resin containing a filler such as talc.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to FIGS. A mudguard for automobiles is used as an example of a plastic molded product. FIG. 1A is a perspective view of the mudguard 1, and FIG. 1B is a cross-sectional view taken along line AA of FIG. 1A. In FIG. 1B, 2 indicates a soft material, and 3 indicates a hard material. Reference numeral 4 denotes a bolt mounting hole, and the periphery of the bolt mounting hole 4 is held with high rigidity by a hard material 3 as shown in FIG.

FIG. 2 shows a front view of the mud ghat 1 and FIG.
Reference numeral a denotes an attachment portion in which the bolt insertion hole 4 is arranged, and is reinforced with the hard material 3 as described above. 1b is a flap portion made of the soft material 2. FIG. 3 shows a part of a forming device 10 for the mudguard 1, that is, a portion for forming a mounting portion 1a (cross section taken along line BB in FIG. 2) including the bolt mounting hole 4. Molding device 1
Numeral 0 has a fixed mold 11 and a movable mold 12, and each mold is provided with circular projections 13 and 14 facing each other, and a thin slit 15 is formed between the tips. . The positions of the circular protrusions 13 and 14 correspond to the positions of the bolt mounting holes 4 of the mounting portion 1a of the mudguard 1, and the diameter of the circular protrusions 13 and 14 is 2/10 of the diameter of the bolt mounting hole 4.
The size is set to be about 0 mm larger. Circular protrusion 1
On the other hand, in the present embodiment, the circular protrusion 13 is provided with a resin press-fitting passage (sprue or runner) 16 communicating with the slit 15. Therefore, the slit 15 becomes a gate communicating with the sprue or the runner 16. Reference numeral 17 denotes a cavity formed between the fixed mold 11 and the movable mold 12.

In the above configuration, first, the resin press-fitting passage 16
Of the soft material 2 from the cavity 17 through the slit 15
, And then the hard material 3 is injected into the cavity 17. Both the soft material 2 and the hard material 3 penetrate into the cavity 17 radially from the slit 15. Injected hard material 3
Flows out of the slit 15 through the soft material 2 and surrounds the circular projection 15. Therefore, the rigidity of the molded product is high around the circular protrusion 15. When the mudguard 1 is taken out of the mold, two circular holes defined by the thin film 18 made of the soft material 2 and the hard material 3 are formed in the mudguard 1 so as to face each other. When the thin film 18 is removed, the two circular holes communicate with each other to form the bolt mounting hole 4, and the periphery thereof is increased in rigidity by the hard material 3 as described above.

[0011]

The present invention has the following advantages because it has the above-mentioned structure. (A) Since the hard material is filled only in the portion where rigidity is required, the hard material is filled in a wide range as in the conventional case. Less deformation than molded products. (B) Since an iron plate insert is not required, the molding cycle can be shortened. (C) The weight of the molded product is reduced, and there is no trace of the holding pin as in the related art, and the appearance of the molded product is improved. (D) The general thickness of the molded product can be freely selected. (E) Damage to the mold is reduced.

[Brief description of the drawings]

FIG. 1A is a perspective view of a mud guard according to an embodiment of a plastic molded product. (B) is a sectional view taken along line AA of (a).

FIG. 2 is a front view of a mudguard.

FIG. 3 is a sectional view of a mudguard forming apparatus.

FIG. 4 is a perspective view of a conventional mudguard.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mudguard 2 Soft material 3 Hard material 4 Bolt mounting hole 10 Molding device 11 Fixed mold 12 Movable mold 13 Circular protrusion 14 Circular protrusion 15 Slit 16 Resin press-in path 17 Cavity

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-86510 (JP, A) JP-A-1-269513 (JP, A) JP-A-1-233178 (JP, A) JP-A-5-205 57747 (JP, A) JP-A-5-31756 (JP, A) JP-A-5-84777 (JP, A) JP-A-4-339607 (JP, A) JP-A-4-331119 (JP, A) JP-A-5-154865 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/00-45/84 B29C 33/00-33/76

Claims (1)

(57) [Claims] At a portion of a cavity of a molding die for a plastic molded product corresponding to a bolt mounting hole of the plastic molded product, a circular protruding portion is provided on a fixed mold and a movable mold so as to oppose each other. A molding device for a plastic molded product, characterized in that a slit is formed between the ends of the circular protruding portions, and a resin press-fitting passage that opens to the slit is provided in one protruding portion.