JPS61148023A - Molding method of hollow body - Google Patents

Abstract

PURPOSE:To prevent generation of defective molding due to a matter that premolded materials are come into contact with each other and adhere closely each other, by a method wherein two sheets of flat-platelike premolded materials made of thermoplastic synthetic resin which have been plasticized and molten are placed between holding components whose shapes are corresponding to that of a frame member and split molds are inserted into the frame member from both sides. CONSTITUTION:Molten and flat-platelike premolded materials 7, 7 are arranged between a main mold 1 and a frame member 4, which are made to place among the frame member 4 and holding components 2, 2 by clamping the main molds 1, 1 and space surrounded by the flat-platelike premolded material 7, 7 and the frame member 4 is made into an airtight state. Then mold clamping is progressed and the molds 1, 1 are inserted into the frame member 4 while positional relation between the frame member 4 and holding component 2 is being maintained. Air in the inside of the frame member 4 is pressed by the molds 1, 1, presses the flat-platelike premolded materials 7, 7 and pressure of the inside of the premolded material is improved up to sufficient pressure making the flat-platelike premolded body take a shape of a cavity at the time of completion of the mold clamping.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method of forming a hollow body using two sheets.

Conventional technology In this type of sheet molding, two sheets of molten thermoplastic synthetic resin are placed between split molds, the split molds are tightened, and a blow nozzle placed between the sheets is used to blow the two sheets. A hollow body is formed by blowing compressed air into a sheet and forming a hollow body in the shape of a split mold into the sheet (for example, Japanese Patent Publication No. 44-10397). .

Problems to be Solved by the Invention In this type of sheet forming, as described in the above-mentioned publication, when two sheets are placed horizontally, the molten sheet will sag due to its own weight and the two sheets will intersect with each other. It has the disadvantage that it is difficult to mold a complete hollow body because it comes into close contact with the body. In addition, if two sheets are placed vertically to prevent them from sagging due to their own weight, contact due to sagging can be prevented, but the two sheets may swing during mold clamping and may come into contact with each other in the same way and stick together, especially when molded. If the hollow body to be molded has an intertwined shape as shown in Figure 6, the two sheets will come into close contact with each other before the mold clamping is completed, and the hollow body will be completely molded. The drawback was that the two sheets in the hollow part were in close contact with each other, making it impossible to form a sufficient hollow body.

Means for Solving the Problems Therefore, the present invention provides the following steps: A frame body surrounding the four sides is interposed between two flat plate-shaped preforms of plasticized and melted plasticized synthetic resin, and then this flat plate-shaped preform is The body is sandwiched between holding members having a shape corresponding to the frame body, a split mold is inserted into the frame from both sides, and the split mold is closed while maintaining the pressure inside the flat plate-shaped preform above atmospheric pressure. to produce a hollow body.

This configuration is intended to solve the above-mentioned conventional problems.

In other words, the present invention interposes a frame surrounding the two flat preforms on all sides between the two flat preforms, thereby giving the two flat preforms a certain distance so that they do not come into contact with each other before the completion of molding. Then, the two flat plate-shaped preforms are sandwiched and held by a holding member having a shape corresponding to the frame, and the preforms are compressed with a split mold and molded. Therefore, even if the pressure inside the preform exceeds atmospheric pressure and the split molds approach each other and mold clamping progresses, the two plate-shaped preforms will not come into contact with each other due to the above pressure, and the mold will close. It is only when the tightening is completed that they come into contact and stick together.

Example Embodiments of the present invention will be described below based on the drawings.

A fishing net buoy a formed according to the present invention is shown in FIG. This buoy a is used to know the position of a fishing net when it is set in the sea, and it does not sink in seawater and uses its own buoyancy. This buoy a is
It has a spherical shape as a whole, and the inside is hollow and sealed. A part of it has a hole Ct4 for fixing it to a fishing net.
It has a solid flat plate part.

FIG. 1 shows an overall perspective view of an apparatus for implementing the present invention. 1, 1 is a main mold. The cavity 3.3 of the main mold 1.1 is recessed to have the outer shape of the buoy a. A frame body 4 surrounding the four sides is fixedly held between the main body molds 1.1 by means not shown. In addition, around the main mold 1.1, a holding member 2゜2 having a shape corresponding to the frame 4 is protruded from within the main mold 1.1 to the side of the mold mating surface or slightly toward the frame 4. When the mold is opened as shown in Fig. 1, the mold body 1 and the holding member 2 are placed in a position that is flush with or slightly protrudes from the cavity surface due to the tension 5 between the main mold 1 and the holding member 2. It is configured.

Reference numerals 6, 6, . . . are deaeration holes, which communicate from the inside of the cavity 3 to the outside of the mold.

The process of forming the buoy a will be explained in order with reference to FIG. 2 and FIG. 4.

First, a molten plate-shaped preform 7.7 is placed between the main mold 1 and the frame 4. The preform 7.7 can be produced by using a known technique, for example, by heating a preform previously formed into a flat plate shape during molding to form the melted flat preform 7, or by heating and melting the preform. It can be easily arranged by techniques such as extruding the body through a die to form a flat plate. The preform used here can be made of thermoplastic resin such as polyethylene, polypropylene, polyvinyl chloride, etc. (FIG. 2).

Next, the main mold 1.1 is tightened to form the flat plate-shaped preformed body 7.
．． 7 is sandwiched between the frame 4 and the holding members 2, 2, and the portion surrounded by the flat plate-shaped preforms 7, 7 and the frame 4 is made substantially airtight (Fig. 3). ).

Further, as the mold is tightened, the main mold 1 is tightened while maintaining the positional relationship between the frame 4 and the holding member 2 by the action of the spring 5.
．． 1 into the frame 4. When the main body molds 1, 1 are inserted into the frame 4, the air in the frame 4, which is made substantially airtight, is compressed by the main body molds 1, 1, and the air is compressed by the main body molds 1, 1, and a flat preform 7 is formed. 7, and at the end of mold clamping, the pressure inside the preform is high enough to shape the cavity into a flat plate-like preform. If the pressure at this time is above atmospheric pressure, sufficient molding is possible in this example, but if the shape is complex unlike the spherical shape as in the above example, the pressure may be 2 kg/cr& or more. I like it. At this time, the air between the preformed body 7 and the cavity 3 is evacuated through the deaeration holes 6, 6, . . . . The inside of the molded buoy is sealed and hollow, and the pressure inside this is at least at least atmospheric pressure (Figure 4).

In addition, although a cylinder was used in the above embodiment, it is also possible to use a cylinder to protrude the holding member and sandwich the preform. This has the advantage that the timing can be freely selected since the timing can be applied electrically.

In addition, in the above example, the shape of the cavity of the split mold was formed by the sealed pressure in the two flat plate-shaped preforms, since the obtained hollow body was a closed-shaped fishing net buoy. However, the present invention is not limited to these, and it is also possible to interpose a blowing nozzle between two flat plate-shaped preforms and spray pressurized fluid from the blowing nozzle at the end of mold clamping to perform molding. It is.

Furthermore, the shape of the cavity of the split mold can be shaped more effectively by actively sucking through the degassing holes of the above embodiments. FIG. 6 shows case d, which is another embodiment obtained by implementing the present invention.

This case d consists of a main body e and a lid f.
It has a handle g that is integrally provided. Body e.

The lid f and the handle g each have a hollow part, h'
.

The case d has a storage recess j in the main body e and the lid f, and the contents are stored in the storage recess when the case d is closed. In order to manufacture this case d, it is also possible to actively pressurize the preform by ejecting pressure fluid with a blow nozzle, but as in the above embodiment, the blow nozzle is not used and the preform is If the molding is done using internal pressure, the molding can be done without forming a blowing hole by the blowing nozzle, so the hollow part i is sealed and the storage recess j increases the cushioning properties, creating a case with extremely good cushioning properties. You can get it.

Effects of the Invention As described above, according to the manufacturing method of the present invention, two arranged preforms do not come into close contact with each other before the molding is completed, and even hollow bodies with complicated walls can be preformed. It is possible to mold the material very easily without causing molding defects due to close contact between the bodies.

[Brief explanation of the drawing]

Fig. 1 is an overall perspective view of the device used for carrying out the present invention;
Figure 4 is a side view for explaining the present invention in detail;
The figure shows the process of placing the preform, Figure 3 shows the process of sandwiching the preform between the movable molds, Figure 4 shows the process when the main mold is fully tightened, and Figure 5 shows the process of clamping the preform with the movable mold. FIG. 6 is a perspective view of a fishing net buoy according to an embodiment of the present invention, and FIG. 6 is a perspective view of a case according to another embodiment of the present invention.

Claims (1)

[Claims] A frame body surrounding the four sides is interposed between two flat preformed thermoplastic synthetic resin sheets that have been plasticized and melted, and then this flat preformed body is held by a holding member having a shape corresponding to the frame body. A split mold having the outer shape of the hollow body in its cavity is inserted into the frame from both sides, and the split mold is closed while maintaining the pressure inside the flat preform above atmospheric pressure to form the hollow body. A method for forming hollow bodies.