JPH07195507A - Mold for molding foamed sheet - Google Patents

Abstract

PURPOSE:To well form a heated foamed sheet into an outline shape by air- pressure forming immediately before forming the same into a final shape by vacuum molding using a cavity mold. CONSTITUTION:A cavity mold is constituted of a plug mold 20 and a recessed part 22 is formed to the central part of the mold so as to foot a protruding part 23 to the peripheral part of the recessed part 22. A compressed air sending hole 21 for air-pressure molding is formed to the mold at the position of 60% or less of the height of the mold and the height (a') of the mold is set to the range of 70-90% of the depth of a molded product. Therefore, the contact surface of the mold with the foamed sheet is reduced to improve the elongation of the sheet and the draw-in quantity of the sheet can be made proper by the height range of the mold or the position range of the compressed air sending hole and air-pressure forming effect is enhanced to eliminate the irregularity of wall thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal mold for forming a foamed sheet, and more particularly to a plug mold suitable for performing pressure molding in a general shape before vacuum molding by a cavity mold.

[0002]

2. Description of the Related Art Conventionally, in the case of forming a deep molded product from a foamed sheet, that is, a container molding, a vacuum molding using a cavity mold is carried out as a method for molding a molded product having a depth of 0.5 times or more of a diameter. Previously, we have tried to make the wall thickness of deep-formed products as uniform as possible by forming into a general shape using a plug mold.

A concrete example of prior art is shown in FIGS. 5 (1) to 5 (3). Prior to final molding of the cavity mold 50 by vacuum, first, from the air supply hole 61 for compressed air of the plug mold 60. The foamed sheet S is lifted and expanded by the plug mold 60 in the compressed air to form a schematic shape, and then the cavity mold 50 is formed.
Vacuum forming is performed while vacuum suctioning.

[0004]

However, in the conventional plug mold, since the foamed sheet S is in contact with the entire upper surface portion, cooling progresses in that portion and the elongation deteriorates.
Therefore, when a vacuum is applied, the other parts are stretched and thinned. In particular, the side portion becomes thin, and a difference in wall thickness between the bottom portion and the side portion occurs. Moreover, since the foamed sheet is lifted on the entire bottom surface, the pull-in rate also becomes large, and there is a problem that the pull-in amount at the side portions becomes too large.

Therefore, an object of the present invention is to provide a mold for forming a foamed sheet which can solve the above-mentioned problems of the prior art.

[0006]

As a mold for forming a foamed sheet according to the present invention which can achieve the above object, a heated foamed sheet is compressed into a general shape immediately before vacuum forming into a final shape by a cavity mold. A plug mold for molding, in which a concave part is formed in the center of the upper part of the mold and the peripheral part is formed as a protrusion, and a pneumatic air supply hole is provided at a position of 60% or less of the mold height. It is characterized in that it is formed, and the height of the mold is formed within the range of 70 to 90% of the depth of the molded product.

[0007]

The above-mentioned mold for forming a foamed sheet according to the present invention, that is, the plug mold, lifts a heated foamed sheet,
Performing a compressed air action from the air supply hole for compressed air to mold it into a general shape like a balloon is inflated, but since a recess is formed in the center of the upper part of the mold and only the protrusion around the upper part contacts the foam sheet, Even when the foamed sheet is lifted by the plug mold, only a few contact parts remain slightly thicker, and the other parts will be stretched uniformly with less temperature drop of the foamed sheet, and local to the foamed sheet. Because it is lifted, the amount of retraction does not increase too much.

Moreover, since the air supply holes for compressed air are formed at 60% or less of the height of the plug mold, if the conventional position is maintained, the vicinity of the bending boundary between the side part and the bottom part of the molded product will occur. It also works well to prevent it from being stretched extremely thin in compressed air, preventing variations in wall thickness. Furthermore, since the height of the plug die is within the range of 70 to 90% of the depth of the molded product, the amount of pull-in is not too small or the amount of pull-in is too large so that a crack occurs on the side, so that a suitable amount of meat can be obtained. Can be formed to a thick thickness.

[0009]

EXAMPLES Examples of the present invention will be illustrated below with reference to the drawings. FIG. 1 shows a plug mold 20 which is a mold for forming a foamed sheet according to the present invention.
(3) shows a molding process using this, and the height a ′ of the plug mold 20 is 0.7a to 0.9a with respect to the depth a of the final molded product by the cavity mold 10. It is formed to a height within the range. Reference numeral 21 denotes an air feeding hole for compressed air, which is formed within the range of the position d of 60% or less of the plug mold 20 to prevent the vicinity of the boundary between the side and bottom of the molded product from becoming extremely thin. There is.

A recess 22 is formed in the center of the upper portion of the plug mold 20, and a peripheral portion is formed as a protrusion 23, so that the entire upper surface of the plug mold 20 is prevented from coming into contact with the foamed sheet S. ing. Further, the height a'of the plug mold 20 is formed within the range of 70 to 90% of the height a of the molded product, so that the seat pull-in amount can be appropriately maintained. Then, the heated foamed sheet S is lifted by the plug mold 20, and after being formed into a schematic shape by the pneumatic molding from the air-pneumatic air supply hole 21, the cavity mold 10 is vacuum-formed into the final molded product. I do.

A foamed polypropylene sheet is suitable as the foamed sheet S used for the above-mentioned molding, but it goes without saying that it can be applied to other foamed sheets. In the foam sheet molding die of the present invention, as shown in FIG. 3 (1), only the portion B of the protrusion 23 contacts the foam sheet S, and the portion C does not contact and is not cooled. If it is left as 61, the C portion is cooled and does not extend, and the other portion is excessively extended and becomes extremely thin. That is, conventionally, as shown in FIG. 3 (2), the portion A, which is the entire upper surface bent from the side, comes into contact with the foamed sheet S, and the foamed sheet S is cooled, so that the elongation is partially extremely deteriorated.

A concrete comparison of the case of the molded product shape as shown in FIG. 4 shows the result obtained by averaging the wall thicknesses at each of the points from the upper edge to the bottom in the case of the molded product shape as shown in FIG. The case of the invention and the conventional example are shown below. The raw material used has a basis weight of 500 g / m ² and a primary thickness of 1.
It is a 3 mm expanded polypropylene sheet (trademark: Neomicrolen).

Molded product using the mold of the present invention Molded product using the conventional mold 0.80 0.76 0.50 0.52 0.52 0.48 0.92 1.03 0.48 1.18 0. 73 1.32 Average 0.66 Average 0.88 Standard Deviation 0.17 Standard Deviation 0.31 As described above, it was found that the molded product using the mold of the present invention can be formed to have an averaged thickness as a whole.

[0014]

As described above, according to the mold for forming a foamed sheet according to the present invention, the contact with the foamed sheet is reduced as a plug mold to improve the elongation, and it is easy to perform pressure molding in a general shape, and vacuum forming is performed. The mold is suitable for molding immediately before, and the amount of the foamed sheet drawn can be appropriately maintained, and the mold is suitable for providing a foamed sheet molded product having a stable and uniform thickness.

[Brief description of drawings]

FIG. 1 (1) is a plan view of a mold of the present invention. (2) is a sectional view of the same as above. (3) is a side view of the same.

FIG. 2 (1) is a sectional view before pressure forming. (2) is a cross-sectional view at the time of pressure molding. (3) is a cross-sectional view at the time of final forming by vacuum forming.

FIG. 3 (1) is a schematic half cross-sectional view showing the upper surface side contact with the foamed sheet of the mold of the present invention. (2) is a schematic half cross-sectional view showing a conventional mold in comparison with (1) of FIG. 3 above.

FIG. 4 is a cross-sectional view showing a shape example of a foamed sheet molded product.

5 (1) to (3) are cross-sectional views of the steps of using the conventional mold, in comparison with (1) to (3) in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Cavity mold 20 Plug mold according to the present invention 21 Pneumatic air supply hole 22 Recess 23 Protrusion

Claims (1)

[Claims] 1. A plug mold for press-molding a heat-foamable sheet into a general shape immediately before vacuum forming into a final shape by a cavity mold, wherein a concave portion is formed at the center of the upper part of the mold. It is formed, and the peripheral part is formed as a protrusion, and a pneumatic air supply hole is formed at a position of 60% or less of the height of the mold, and the height of the mold is 70 to 9 times the depth of the molded product.
A mold for forming a foamed sheet, which is formed within a range of 0%.