JPS592610B2 - Pressing method for plastic sheets - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a press working method for obtaining a plastic sheet product having a concave portion with an upper concave portion such as a reverse taper.

Conventionally, when molding products with various uneven shapes from plastic sheets by press working, the recesses in the product, such as grooves and holes, have a tapered shape that widens toward the top opening, or at least the inner surface of the recess or It was only possible to mold products with a vertical inner circumferential surface.

In other words, in conventional press working, both the female die and the male die use molds that are rigid as a whole, so if the concave part of the female die is made into a reverse tapered shape with an upward convergence, the protrusion of the male die also corresponds to this. If the plastic sheet is pressed, it will be impossible for the male convex part to enter or exit the female concave part, so in practice the grooves, concave holes, etc. have to be formed into a tapered shape that expands slightly upward. . However, depending on the application, for example, there may be cases where it is desired to mold a holding frame with a holding groove with a slightly narrowed upper opening side from a plastic sheet so that it can elastically hold solid paints, syringes, etc. in a removable manner. However, it has not been possible to satisfy these demands with the conventional press working techniques as described above. In view of these circumstances, it is an object of the present invention to provide a method for easily forming a processed plastic sheet product having an upper narrowed portion such as a reverse taper in the recessed portion by press working. Embodiments of the present invention will be described with reference to the drawings. Figures 1a to 1e schematically show the method of the present invention. In the figures, 1 is a female mold, which is a rigid mold made entirely of iron, etc. The recess 2, such as a groove or a recessed hole, is formed into an inner arcuate shape or a reverse tapered shape with a narrower width or diameter to some extent near the upper end opening (this recess 2 is hereinafter referred to as a special recess).

3 is a male mold with a shape corresponding to the female mold 1, and a synthetic resin or rubber with high heat resistance and elasticity, such as silicone rubber or rubber mixed with fibers, is applied to the part corresponding to the special recess 2. The elastic protrusion 4 used is provided.

The elastic protrusion 4 is formed by covering the tip of the iron core 5 with an elastic material as described above in a shape corresponding to the special recess 2 . As this elastic material, silicone rubber is particularly preferable because it has good elasticity and high heat resistance, and the surface of this silicone rubber etc. is coated with Teflon to prevent the plastic to be processed from adhering. It is desirable that the two dies 1 and 2 be used for press working. First, as shown in FIG. With the sheet 6 interposed, in this state, the sheet 6 is heated to an appropriate temperature by any means to soften it, the male die 1 is brought close to the female die 2, and the sheet 6 is pressed.

At this time, the vinyl chloride sheet 6 will soften if heated to about 150 to 160°C, whereas the elastic protrusion 4 can withstand up to a mixing temperature of about 300°C if silicone rubber is used, so it can withstand the above heating. It never changes in quality. During this pressing process, the elastic protrusion 4 pushes the sheet 6 into the special recess 2 and is elastically deformed when passing near the narrow opening of the recess 2 as shown in FIG. 1b. As shown in FIG. 1c, when the sheet 6 is completely pushed into the recess 2, the restoring force brings the sheet 6 into close contact with the inner surface of the recess 2. As a result, the sheet 6 is softened and plastically deformed into a shape that conforms to the recess 2. Next, after holding this state for several seconds, the female die 3 is separated from the female die 1 as shown in FIG. to separate from Further, the heat-pressed sheet 6 is cooled down to a level where it will not be plastically deformed, and then released from the female mold 1 by utilizing its own elastic deformation. A sheet workpiece 6' having a narrowed upper concave portion 7a is formed (see FIG. 1e). An example of a processed molded product to which the method of the present invention is applied and a specific press processing method corresponding thereto will be described below.

FIG. 2 shows a solid paint holding frame 16 made of a hard vinyl chloride sheet, and the frame 16 removably accommodates a large number of pencil-shaped solid paints 22 in the required parts. It is provided with a solid paint accommodating part 16a for holding solid paint, and further has recesses 16b and 16c for storing erasers, sharpeners, etc. in the remaining part as necessary.
It is equipped with

The solid paint storage section 16a has a partition wall 18 in the shape of a protrusion.
A large number of solid paint holding grooves 17 arranged in parallel through...
and deep recesses 19 and 20 provided outside both ends of the grooves 17 to facilitate the operation of taking out the solid paint. Each of the grooves 17... is provided with an inverted tapered upper part 17a... near the upper end opening, and this part 17a... makes use of the elasticity of the material to solidify the material. The paint 22... can be attached and detached at will, and the frame 1
6 is kept in a state where it will not come off unexpectedly even if it is reversed. In this case, the upper narrowed portion 17a may be provided over the entire length of the groove 17, but as shown in the figure, it is actually better to provide it partially at both ends of the groove 17. It facilitates pressing work, mold cutting work, etc. during processing by the method of the invention, and also makes solid paint 2 easier to use.
This is preferable in that it facilitates the attachment and detachment of 2.... and,
This frame 16 is a container main body 21, for example, which is formed by connecting a bottom plate 21a and a top lid 21b via a gusseted bent part 21c on one side.
By being fixed to the upper surface of the bottom plate 21a inside the main body 21, it constitutes a solid paint storage container. When molding this solid paint holding frame 16 by press working, the female mold 11 has the fixed paint holding groove 17 and
The required number of special recesses 12 in parallel for forming...
..., and the whole is formed in a shape corresponding to the frame 16 to be molded. On the other hand, the male mold 13 has the grooves 17...
The above-mentioned grooves 1
7. Apply silicone rubber, etc. to the molded part of the iron core 15.
It is formed by attaching the elastic protrusion 14 provided on... In this case, the elastic body 145 such as silicone rubber is normally installed in a continuous state at the base even if it is between the protrusions 14, and the iron core 15 is attached to the mounting base. 155 etc., and the iron core 15...
Protrusions 15a are provided on both sides of the elastic body 1.
4' can be slidably attached to and detached from the iron core 15 from the side end in the longitudinal direction, so that when the elastic body 14' reaches the end of its useful life, it can be replaced at will.
As a means for forming the elastic body 14' into a predetermined shape,
Although not shown, a pre-molten material such as silicone is poured into a base mold having the same shape as a predetermined portion of the female mold 11, with the iron core 15 inserted to a predetermined position, and then solidified. It is only necessary to elastically release the mold from the base mold after the molding. Then, by using such female die 11 and male die 13, a solid paint holder having the solid paint holding grooves 17 is formed from the plastic sheet 6 in the same manner as the method based on FIG. 1 described above. 16 can be press-molded.
The press working method of the present invention is not only used for forming the solid paint holding frame 16 described above, but also for attaching and detaching cylindrical or polygonal objects such as syringes and ampoules. Furthermore, it is used as a container or frame to hold the container or frame so that it does not come off unexpectedly, when a plastic sheet is molded into a structure with a holding groove that tapers at the top.

Furthermore, according to the method of the present invention, in addition to the above embodiments,
For example, as shown in FIG. 6, it is possible to mold a plastic sheet workpiece 26 in which the inner surface of the recess 27 is partially provided with protrusions 27a or recesses. By designing the shape according to the shape of the intended product, it is possible to mold various plastic sheet products having at least a certain degree of upper narrowing in the recess. As mentioned above,
In the press working method of the present invention, a female mold having a special concave portion having a narrowed upper portion is used, and a material with high heat resistance and elasticity such as silicone rubber is used for the male mold to provide elasticity corresponding to the special concave portion. By providing the protrusion, the elastic protrusion is pushed into the special recess together with the heated and softened sheet by utilizing the elastic deformation of the protrusion, and the restoring force of the protrusion causes the inner surface of the special recess to be pushed into the special recess. After the sheet is plastically deformed into the desired shape, the elastic protrusion is extracted from the special recess, which eliminates the upper constriction that could not be formed by conventional press processing using a mold that is entirely rigid. It is possible to easily process and mold a plastic sheet product having a recessed portion having a recessed portion, and the field of use of press processing can be greatly expanded, resulting in great practical effects.

[Brief explanation of drawings]

The figures show examples of the present invention. Figures 1a to 1e are explanatory diagrams showing the method of the present invention in the order of steps, and Figure 2 is a solid paint holding frame molded using the method of the present invention. Perspective view of 3rd
The figure is a partial enlarged cross-sectional view taken from the - line in Figure 2, Figure 4 is a cross-sectional view of the main part showing the shape of the mold used for molding the frame, Figure 5 is a perspective view of the main part, and Figure 6 The figure is a sectional view showing another example of the shape of a recessed part of a processed product formed using the method of the present invention. 1,11...Female type, 2,12...Special recess, 3,13...Male type, 4,14...
- Elastic protrusion, 6...Plastic sheet.

Claims (1)

[Claims] 1. Equipped with a female mold having a special concave part with a tapered upper part such as a reverse taper, and an elastic protrusion corresponding to the special concave part made of synthetic resin or rubber with high heat resistance and elasticity such as silicone rubber. with the male die facing each other, and with a plastic sheet for processing interposed between the two dies,
By bringing the male mold close to the female mold while heating and softening the sheet, the elastic protrusion of the male mold is elastically deformed into the special recess of the female mold, and the restoring force of the rear projection pushes the sheet into the special recess. Then, by separating the male mold from the female mold, the elastic protrusion is pulled out from the special recess, and the workpiece is cooled and then released from the female mold to form a reverse tapered part, etc. A method for pressing a plastic sheet, characterized by obtaining a processed plastic sheet product having the following properties.