JPH044134B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a method for molding concave hollow or double-walled plastic molded products, such as hollow or double-walled containers, tanks, etc. The present invention relates to a molding method particularly suitable for molding concave hollow or double-produced plastic molded products with shapes that cannot be obtained or are extremely difficult to obtain from tube parisons, such as defective products, thick walls, and different colors.

[Conventional technology and its problems]

Special types of concave hollow or double-layered plastic molded products, such as large and flat types, cannot be molded using traditional blow molding or vacuum molding using split molds rather than tube parisons. Due to the peculiarity of the shape, the partial thinning of the tube parison during molding is too large, resulting in damage to the polyson or a molded product whose wall thickness is so extremely thin that a portion of the tube parison cannot be put to practical use. This tendency is particularly noticeable in the case of deep ones.

Furthermore, if this type of molded product has a hollow or double structure with a concave outer wall and inner wall of different colors or different wall thicknesses, it cannot be molded from a tube parison using conventional molding methods.

Even if a sheet parison is used, the molding of such a special type of concave hollow or double-structure molded product cannot be effectively realized by conventional blow molding or vacuum molding using a split mold.

That is, if a special type of concave hollow or double-structure molded product as described above is formed from a sheet parison by conventional blow molding or vacuum forming using a split mold, the following problems occur.

When the male and female molds are closed in order to blow mold or vacuum form a sheet parison, the front surface of the core portion of the male mold comes into contact with the facing portion of the sheet parison at the beginning of the mold closing, and this core portion The sheet parison in contact with the front surface (temperature of about 180℃) is cooled due to the low temperature of the front surface of the core (as is well known, the mold is cooled to about 40℃), loses its formability, and the mold When blow forming or vacuum forming is performed after closing, the forming pressurization or negative pressure is intensively applied to other parts of the sheet parison, and forming progresses in such a way that only the other parts extend, resulting in thinner walls. Therefore, in the same sheet parison, there is a considerable difference in the thickness of the other parts from the part where the moldability has been lost, and it is impossible to obtain a good molded product.

Therefore, the present invention aims to provide a molding method particularly suitable for molding the special type of concave hollow or double-structured plastic molded product as described above.

[Means for solving problems]

The method for molding a concave hollow or double-layered plastic molded product of the present invention involves supplying a first sheet-like molding material to the space between the male mold and the female mold below the mold opening;
between the front surface of the core portion of the male mold and the sheet-like molding material, and between the parting line surface of the female mold and the sheet-form molding material facing thereto, or at least the front surface of the core portion of the male mold. The sheet-like molding material is molded into the female mold by advancing the male mold and/or the female mold, with a barrier of heated air interposed between the sheet-form molding material and the sheet-form molding material. The concave mold is pressed into the cavity and negative pressure is applied to the suction hole of the molding cavity of the female mold to form the outer wall equivalent of the hollow or double structure molded product, and then the male and female molds are The mold was opened and a second sheet-shaped molding material was supplied into the space between them, and a barrier made of heated air was interposed between the front surface of the core part of the male mold and the sheet-shaped molding material. male under condition,
The female mold is closed, and negative pressure is applied to the through hole in the mold surface of the male mold to form the inner wall equivalent of the concave hollow or double structure molded product, and the male and female molds are closed. Under the tightening,
The feature is that pressurized air is blown into the hollow part of the concave hollow or double structure molded product, which is to be integrated into a single unit of the outer wall equivalent and the inner wall equivalent, and molded into the final molded product. There is.

[Operation] According to the present invention, when molding the outer wall equivalent of the concave hollow or double structure molded product from the first sheet-like molding material, at least one of the male and female molds is advanced. At this time, between the front surface of the core part of the male mold and the first sheet-like molding material, and between the parting line surface of the female mold and the molding material facing this, or at least the parting line of the male mold core part. Since a barrier of heated air is interposed between the front surface and the sheet-shaped molding material, the first sheet-shaped molding material is formed by the relative advancement of the male and female molds under the barrier of heated air. , it is pushed into the molding cavity of the female mold without contacting the front surface of the male mold core part and the parting graphing surface of the female mold, or at least the front surface of the male mold core part at the initial stage of mold closing,
Therefore, the outer wall of the concave hollow or double-structured molded product does not undergo partial thinning due to partial preliminary contact with the mold, and is capable of applying negative pressure to the suction hole of the molding cavity of the male mold. The molded product is molded into a concave molded product with equal wall thickness at each part according to the female molding cavity. Note that if a heated air barrier is not interposed between the parting line surface of the female mold and the sheet-shaped molding material of the part facing it, that part of the sheet-shaped molding material will be placed on the parting line surface of the female mold. Although contact occurs prior to molding the material into a predetermined shape, there is no substantial problem. This is because the female mold parting line surface is not the molding cavity or molding surface, and it is important that the sheet-like molding material be molded with a uniform thickness at the portion corresponding to the molding cavity or molding surface.

In the present invention, when molding the inner wall equivalent of a concave hollow or double structure molded product from the second sheet-like molding material, when closing the male and female molds, the female mold Since a heated air barrier is interposed between the front surface of the core portion of the mold and the second sheet-like molding material, the molding material does not come into contact with the front surface of the male mold core portion at the initial stage of mold closing. Therefore, the second sheet-like molding material is molded into a concave-shaped molded product having uniform thickness at each part according to the mold surface of the male mold by applying negative pressure to the through hole of the mold surface of the male mold.

When the mold closing progresses to a certain stage and the above-mentioned outer wall equivalent and inner wall equivalent are combined and integrated into a single unit, under the mold closing of the male and female molds, the uniting process is carried out. The molding of the final molded product is completed by blowing pressurized air into the hollow part of the concave hollow or double-structured molded product.

〔Effect of the invention〕

As described above, the present invention provides a first sheet-like molding material for molding an outer wall equivalent of a concave hollow or double-structure molded product, and a second sheet-like molding material for molding an inner wall equivalent of a concave hollow or double-structure molded product. The molding material is used to prevent the molding material from coming into contact with the front surface of the female mold core at the initial stage of mold closing.
It can be molded into a molded product with a predetermined concave shape and uniform thickness at each part.

Furthermore, in the present invention, as described above, when the male and female molds are closed, the first sheet-like molding material can be pushed into the molding cavity of the female mold to perform molding, so negative pressure is applied to the molding cavity of the female mold. Molding is more effective than relying only on addition.

In the present invention, the first sheet-like molding material and the second sheet-like molding material are molded separately before reaching the final molding stage.
Even if the concave molded product has a hollow or double structure, the outer wall and the inner wall have different wall thicknesses (for example, either the inner or outer wall may be thick or made of an elastic material containing synthetic rubber). This can be molded without any problem. Of course, there is no problem if the outer wall and the inner wall are of different colors, or if the inner and outer walls are integrally welded face-to-face.

The present invention can thus provide a molding method that is particularly suitable for the special type of molding described above for concave hollow or double-walled plastic moldings.

〔Example〕

Next, embodiments of the present invention will be described with reference to the accompanying drawings.

The molding apparatuses illustrated in the drawings used to carry out the method of the present invention include an extruder A, a die B for extruding the first and second sheet-like molding materials 5 and 6, a molding material plasticizing device C, and a mold clamping device. It is equipped with a device D, an extrusion cylinder E, a female mold 1, and a male mold 2.
has an absorption hole 7 opening into its molding cavity 9, and the male mold 2 has a through hole 8 opening into its mold surface 4. The female mold 1 is fixed to the tip of the hydraulic rod 3 in the mold clamping device D, and the male mold 2 is fixed to the tip of the hydraulic rod 3 in the mold clamping device D.
It is attached to a surface plate 15 at the tip of another hydraulic rod 3a.

Male mold 2 and female mold 1 in open state (Figure 1)
Then, the first sheet-shaped molding material 5 is extruded from the die B into the space between the male mold 2 and the female mold 1 under the mold opening on the X-X line, and the male mold 2 and/or the female mold 1 are The mold 1 is advanced, thereby forcing the sheet-like molding material 5 into the molding cavity of the female mold 1 (FIG. 3). At this time, a barrier made of heated air is provided between the front surface of the male mold core and the first sheet molding material 5 so that the first sheet molding material 5 does not come into contact with the front surface of the male mold core. let The provision of this barrier by heated air is achieved by connecting a heated air source to a through hole 8 opened in the front surface of the male mold mold surface 2, and from the front surface of the male mold mold surface 2 through the ventilation hole 8 as shown in the arrow in FIG. This can be done by blowing out heated air in the direction 2a.
If necessary, a through hole opening in the parting line surface 1a of the female mold 1 is provided, and heated air is blown forward from the parting line surface 1a through the through hole to form the parting line surface 1a.
A barrier made of heated air may be interposed between a and the sheet-shaped molding material 5 in the portion facing it.

When the first sheet-like molding material 5 is pushed into the molding cavity 9 of the female mold 1 to an appropriate stage, negative pressure is applied to the suction hole 7 of the molding cavity 9 of the female mold 1 to The sheet-like molding material 5 is used to mold an outer wall equivalent of a concave hollow or double-structure molded product.

Then, the male and female molds are opened, and the second sheet-shaped molding material 6 is extruded from the die B on the Xa-Xa line into the space between them (Fig. 4), and the male mold 2 and/or The female mold 1 is closed so that the outer wall of the concave hollow or double structure molded product on the molding cavity 9 of the female mold 1 covers the male mold core, and a second sheet-like molding is performed. The material 6 is pressed into the molding cavity 9 of the female mold 1 (FIG. 5). At this time, a barrier made of heated air is interposed between the front surface of the male mold core portion and the second sheet molding material 6 so that the second sheet molding material 6 does not come into contact with the front surface of the male mold core portion. This barrier created by heated air is
It may be applied by a method similar to that described above. In FIG. 4, an arrow 16 indicates the direction in which heated air is blown out.

When this mold closure reaches an appropriate stage, negative pressure is applied to the through hole 8 of the mold surface 4 of the male mold 2, and the second sheet-shaped molding material 6 is used to form a concave hollow or double-structured molded product. Molding the inner wall equivalent.

As the mold closes, the outer wall equivalent from the first sheet-like molding material 5 and the inner wall equivalent from the second sheet-like molding material 6 come together and become a single unit. , under the clamping of female molds 1 and 2,
A pressurized air injection needle 12 is pierced into the concave hollow or double structure molded product that is to be integrated into a single unit, and the injection needle 1
Pressurized air is injected into the hollow part 13 of the molded product from the air cylinder 11 of No. 2 through the injection needle 12 to form the final molded product (FIG. 6). In FIGS. 5 and 6, reference numeral 10 indicates a forming burr.

After the above molding process is completed, the male and female molds 1 and 2 are opened, and a molded product 14 as shown in FIG.
can be released and obtained. Furthermore, if the hollow part of the molded product 14 is filled with a foam such as polyurethane resin (not shown), the heat and cold insulation effects will be extremely enhanced.

[Brief explanation of drawings]

FIG. 1 is a partially longitudinally sectional front view of an example of a molding apparatus used in carrying out the method of the present invention, and FIG.
3 to 6 are front views showing the order of the molding process by the illustrated device including FIG. 1, and FIG. 7 is a partially cutaway perspective view of the molded product by the illustrated device. . 1 is a female mold, 1a is a female mold parting line surface, 2 is a male mold, 4 is a mold surface of the male mold, 5 is a first sheet-shaped molding material, and 6 is a second sheet-shaped molding material , 7 is a suction hole, 8 is a through hole, 9 is a molding cavity of the female mold, and 13 is a hollow part of the molded product.

Claims (1)

[Claims] 1. A first sheet-shaped molding material is supplied into the space between the male mold and the female mold under the mold opening, and the first sheet-shaped molding material is supplied between the front surface of the core part of the male mold and the sheet-shaped molding material, and the female mold. A barrier made of heated air is interposed between the parting line surface of the mold and the sheet-like molding material facing therein, or at least between the front surface of the male mold core part and the sheet-like molding material. , the sheet-like molding material is pushed into the molding cavity of the female mold by advancing the male mold and/or the female mold, and negative pressure is applied to the suction hole of the molding cavity of the female mold by a vacuum source. is added to form the outer wall equivalent of the concave hollow or double structure molded product, and then the male and female molds are opened and a second sheet-shaped mold is placed in the space between them. After supplying the molding material, the male and female molds are closed with a heated air barrier interposed between the front surface of the core portion of the male mold and the sheet-like molding material, and the male mold is closed. The above negative pressure is applied to the through hole on the mold surface of the mold to form the inner wall equivalent of the concave hollow or double structure molded product, and under the mold clamping of the male and female molds, the outer wall equivalent to the above is formed. Pressurized air is blown into the hollow part of a concave hollow or double-structured molded product that is to be integrated into a single unit with an object and an inner wall equivalent, and is formed into a final molded product. Molding method for heavy structure plastic molded products.