JPS5919009B2 - Deep drawing method and device using foam sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for deep drawing a foamed sheet, and is capable of performing deep drawing in a good and easy manner.

Conventionally, when deep drawing is performed using a foam sheet for, for example, container molding, the plug-assist method is a type of vacuum forming in which the heated and softened foam sheet is pushed into a female mold using a plug that serves as a male mold, and vacuum is drawn from the female mold. In addition, there are methods such as pre-stretching in the opposite direction to the female mold and then forming it along the female mold, and methods of blowing air in the direction of the female mold, but in both cases, the material is heated and softened. The foamed sheet comes into contact with various parts of the female mold, and heat is taken away, resulting in poor heat retention.Friction also occurs, further deteriorating molding conditions, making it difficult to mold deep objects, and causing damage to the molded product. The thickness tends to be non-uniform, and the side walls tend to become thinner in case of containers with a cup shape, and it is difficult to edge out the outer shape especially in the case of vacuum suction.

For this reason, methods such as inserting slits in the portion of the sheet corresponding to the periphery of the molded product have been proposed in order to improve the drawing of the foam sheet into the female mold, but this method was extremely troublesome for molding. In addition, the ratio of deep drawing in the conventional method is low (1:
1), which was not suitable for deep drawing.

Therefore, in this invention, it is possible to eliminate the drawbacks and inconveniences of the conventional method as described above.The feature of this molding method is that a foamed sheet made of thermoplastic resin is heated and softened. In the method of intrusion molding into a female mold by a male mold, the foam sheet with both ends open is locally pressed to the center of the bottom of the female mold using a first protrusion mold attached to the male mold main body. a molding step, and then a molding step of expanding the pressing range of the foamed sheet to the vicinity of the bottom of the female mold by a second abutment die attached to the male mold main body in addition to the pressing step by the first abutment die; Furthermore, after going through multiple molding steps in which the pressing range of the foam sheet is expanded in the male mold body to the bottom and peripheral wall of the female mold in addition to the pressing step C by the protrusion mold, the foam sheet still remains in the female mold. This is because the molding is carried out from the beginning of pressing, which does not conform, to the final shape that can conform to the female mold.

Next, embodiments of the method of the invention will be illustrated below with reference to the drawings together with an apparatus of the invention for carrying out the method.

Figures 1 to 3 show the process of forming a kotsubu as a deep drawing product, with 10 being a female die and 20 being a male die. 22 and a first protrusion mold 23.

And inside the storage chamber 2 of the male main body 21,
A small second abutment mold 22 can be stored, and a first abutment mold 23, which is smaller than the second abutment mold 22, can be stored in the storage chamber 22'' of the second abutment mold 22. It's getting old.24
is a first spring provided between the second protrusion mold 22 and the first protrusion mold 23; 25 is a second spring provided between the male main body 21 and the second protrusion mold 22;
The first spring 24 pushes the first protrusion mold 23, and the second spring 25 pushes the second protrusion mold 22 in the projecting direction. This is a moving member, and the repulsive force of the first spring is made weaker than the repulsive force of the second spring, so that the female mold 101fC can be pressed sequentially from the first protrusion mold 23. .

During molding, a foamed sheet a made of a thermoplastic resin, such as a foamed polystyrene sheet, is heated and softened and pressed into the female mold 10 using a male mold 20 VC according to the embodiment shown in FIG. Of these, the first abutment type 23V
C, the foam sheet a with both ends open is still in the female mold 10.
When the male mold 20 is partially pressed into the female mold 10 in a shape that does not follow the VC, and then the male mold 20 is pushed deeper, the first protrusion mold 23 moves the first spring 24 into the storage chamber 22'' where the second protrusion mold 22VC is located.
The foam sheet a is pressed against a wide range by the first protrusion die 23 and the second protrusion die 22, and the foam sheet a is pressed against the pressing force of the female die 1.
The shape is somewhat similar to the shape of 0 (see Figure 2),
When the male die 20 is further pushed in, the second protrusion die 22 moves into the storage chamber 21 of the male die main body 21 against the pressing force of the second spring 25 while storing the first protrusion die 23. The foamed sheet a can be formed into a final shape that follows the shape of the bottom and peripheral wall of the female mold 10 in the male mold main body 21 (
(See Figure 3).

After molding, the molded product A is recovered by releasing the male and female molds 10 and 20.

As described above, in the present invention, the pressure of the male mold 20 for molding the foam sheet AvC is increased or decreased during the process from the beginning of pushing, when the foam sheet a does not yet conform to the female mold 10, to the final shape that can conform to the female mold 10. This is carried out in multiple stages using two protrusion molds 22 and 23.

In addition, when pressing the foam sheet Avc with the male die, although not shown, vacuum suction from the female die side or air blowing in the direction of the female die may also be used. In this case, use a molding device with an appropriate structure.

As the foam sheet a, a foam sheet other than foamed polystyrene may also be used. As mentioned above, according to the method of the present invention, unlike the conventional method, molding along the female mold shape is not immediately performed at the same time as the male mold presses the foam sheet into the foam sheet, but the foam sheet is formed with both ends open by the male mold. Because the sheet is pressed in three stages, it is possible to mold the heated and softened foam sheet without forcing it to be squeezed, so in the case of deep containers, etc., only the bottom side can be molded. This eliminates the drawback that the thickness increases and the peripheral wall side becomes thinner, which helps to equalize the overall wall thickness.

Moreover, since the pressure on the foam sheet by the male die is not applied entirely to the female die, sudden contact of the foam sheet with the die is avoided, thereby preventing frictional build-up and cooling of the sheet temperature, which improves the heat retention of the foam sheet. This means that deep drawing can be carried out smoothly, and it is possible to perform forming with a higher deep drawing ratio than with conventional methods. Moreover, the final shape that conforms to the female die is achieved by the final pressing of the male die, and the edges of the corner portions can also be clearly defined, making it possible to increase the commercial value of the deep-drawn product. In addition, in the device used to carry out the method of the invention, the two protrusion molds installed in the male main body are made smaller toward the female mold, and the smaller protrusion mold is placed inside the larger protrusion mold. When the male mold is pressed into the female mold, the spring that pushes each protrusion mold in the protruding direction sequentially moves the larger male mold from the side closer to the female mold. The foam sheet is designed to be elastically stored in the mold body, and the protrusion-shaped straws close to the female molds are sequentially pressed against the foam sheet with both ends open, so that continuous pressing of the male molds is possible. The deep drawing method described above can be easily carried out by applying the desired multiple stages of pressure to the foamed sheet, and the forming process can be easily performed from a mechanical point of view.

Moreover, the molding device is easy to configure and use, and can contribute to the mass production of deep-drawn products made of foamed sheets.

[Brief explanation of the drawing]

The drawings illustrate an embodiment of the present invention, and FIGS. 1 to 3 are cross-sectional views showing each step during molding, and FIG. 4 is a perspective view showing an example of a deep-drawn product.

Claims (1)

[Scope of Claims] 1. In a method in which a foamed sheet made of a thermoplastic resin is heated and softened and then injected into a female mold by a male mold, the first protrusion mold attached to the male mold main body is a molding step in which the foam sheet with both ends open is pressed locally to the center of the bottom of the female mold, and then a second protrusion mold attached to the male mold body is used to press the foam sheet into the bottom center of the female mold. In addition to the pressing step by the first protrusion mold, the molding step is expanded to the periphery, and the pressing range of the foam sheet is further expanded by the male mold body to the bottom and peripheral wall of the female mold in addition to the pressing step by the protrusion mold. Deep drawing molding using a foamed sheet, characterized in that the foamed sheet is formed through multiple molding stages, including a molding stage in which it is expanded, from the initial stage of pressing when the foamed sheet does not yet conform to the female mold, to a final shape that can conform to the female mold. Method. 2. A deep drawing method using a foamed sheet according to claim 1, which uses vacuum suction from the female mold side when pressing the foamed sheet with the male mold. 3. A deep drawing method using a foamed sheet according to claim 1, in which air is blown in the direction of the female mold when pressing the foamed sheet with the male mold. 4 In an apparatus for press-molding a foamed sheet made of thermoplastic resin into a female mold under heating using a male mold, the male mold main body has a storage chamber capable of storing a smaller second protrusion mold. A storage chamber is provided in the second abutment mold in which a first abutment mold, which is smaller than the second abutment mold, can be stored, and between the first and second abutment molds and Between the male mold and the second protrusion mold, a first spring and a second protrusion mold that push the first protrusion mold in the projecting direction are protruded into the spaces formed in the respective storage chambers. A second spring pushing in the direction is arranged,
The two springs are arranged so that when pressing the male mold into the female mold, the first protrusion mold can be elastically stored in the second protrusion mold and the second protrusion mold can be sequentially stored into the male mold main body. The repulsive force of the first spring is set to be weaker than the repulsive force of the second spring, so that when the foam sheet is open at both ends, pressure is applied sequentially from the first protrusion mold on the side closer to the female mold. A deep drawing device using a foam sheet, characterized by comprising: