JP2853083B2 - Equipment for thermoforming plastic sheets into hemispheres - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for producing a hemispherical body with a picture such as a map used for producing a globe, a celestial sphere, a lunar sphere and the like. It relates to a molding device.

[0002]

2. Description of the Related Art Conventionally, a globe, a celestial sphere, or a lunar sphere is formed by thermoforming a thermoplastic resin sheet 22 on which a map or pattern is printed in advance by using a thermoforming mold to separately form two hemispheres, for example, a northern hemisphere and a southern hemisphere. Then, the two hemispheres are manufactured by bonding or bonding. In order to thermoform the sheet 22 into a hemisphere, a vacuum forming method (see Japanese Patent Publication No. 62-45997) is usually used.
That is, as shown in FIG. 5, a sheet 22 is disposed on the upper surface of a mold 21 having an inner surface formed into a hemispherical surface, and the peripheral portion of the sheet is fixed in a sealed state to the peripheral portion of the upper surface of the mold 21, and the sheet 22 is heated by a heater 24. The mold cavity is evacuated while heating with
As a result, the sheet 22 is brought into close contact with the inner surface of the mold 21 to form a hemispherical body (in FIG. 5, the two-dot chain line indicates the sheet 22 being processed).

In this method, however, the central portion of the sheet 22 being processed receives uniformly the radiant heat radiated from the heater 24, while the peripheral portion is affected by the clamp portion and the outside air (temperature, wind, etc.). As a result, the heat absorption per unit area increases in the central portion, and the peripheral portion of the sheet has a small expansion, and the central portion has a large expansion. The difference in the amount of growth between the peripheral part and the central part has a problem in making the entire surface equal in thickness, and in particular, when manufacturing a product with a picture such as a map such as a globe, the pattern may shift or become discolored, It was not preferable because the center point of the sheet 3 was shifted.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems by providing a device for eliminating the difference in the amount of heat absorbed per unit area between a central portion and a peripheral portion of a sheet. An object of the present invention is to provide a device for thermoforming a new plastic sheet into a hemisphere.

[0005]

In order to achieve the above object, according to the present invention, a thermoplastic plastic sheet 3 is disposed on an upper surface of a mold 2 having a hemispherical concave surface 1 on the upper surface, and a peripheral portion of the sheet is molded by the mold. In this fixed state, the plastic sheet 3 is heated from above by the heater 4 and the inside 5 of the hemispherical concave surface of the mold 2 is brought into a depressurized state, whereby the sheet 3 is brought into close contact with the hemispherical concave surface 1. In the apparatus for thermoforming a plastic sheet into a hemispherical shape, a large number of nets having different diameters are overlapped between the central part of the sheet 3 and the central part of the heater 4 so that the centers thereof coincide with each other. It is equipped.

[0006]

In the embodiment shown in the figures, a mold 2 having a hemispherical concave surface 1 on the upper surface is formed, and a thermoplastic sheet 3 on which a map of the southern hemisphere is printed in advance is placed on the mold 2.
The entire periphery of the sheet 3 is held on the upper surface of the mold 2 by a holding ring 10.
In addition, an outer casing 11 having an open lower surface is provided above the mold 2, and a plurality of far-infrared heaters 4 are provided in the outer casing 11. Are built in as a vertically opposed arrangement, and a vertical bar 12 and a horizontal bar 13 are provided on an open lower surface of the outer casing 11, and large, medium, and small diameter metal grid nets 14 are provided thereon.
15 and 16 are placed in a state where they are overlapped with their center points coincident with each other and in a state where the positions can be changed.

[0007]

The operation of the present invention will be described based on the above embodiment. That is, the outer peripheral portion of the large-diameter net 14 has a single-layer structure, the outer peripheral portion of the medium-diameter net 15 has a double-layer structure, and the entire surface of the small-diameter net 16 has a three-layer structure. is there. Therefore, the heat of the heater 4 passes through the three-layered structure at the central portion of the sheet 3, passes through the two-layered structure at the outer periphery of the central portion, and further passes through the one-layered structure at the outer periphery. And directly at places without a net.

That is, the central portion having a large amount of heat absorbed per unit area described in the prior art is obstructed by the three-layered structure portion, and the outer peripheral portion of the central portion is obstructed by the two-layered structure portion. In this state, heat is received in a state where the outer turning portion is obstructed by the single-layered structure portion, and there is no difference in the amount of heat absorbed per unit area between the central portion and the peripheral portion of the sheet 3.

[0009]

As described above, the apparatus according to the present invention eliminates the difference in the amount of heat absorbed per unit area between the central portion and the peripheral portion of the sheet 3 due to the presence of a large number of nets having different diameters as described above. Thus, it is possible to eliminate the occurrence of misregistration of the picture, the occurrence of the blemishes, and the misregistration of the center point of the picture.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a state in which the sheet is thermoformed into a hemispherical body.

FIG. 3 is a perspective view showing a seat.

FIG. 4 is a perspective view showing the net before being laminated.

FIG. 5 is a sectional view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hemisphere concave surface 2 Die 3 Sheet 4 Heater 5 Hemisphere concave surface inside 7 Hole 10 Holding ring 11 Outer enclosure 12 Vertical bar 13 Horizontal bar 14 Largest net with coarse mesh 15 Medium mesh with coarse mesh 16 Small mesh net 17 Suction hole 18 Clamp

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B29C 51/00-51/46 B29C 49/64-49/68 G09B 27 / 06,27 / 08 B29L 22: 00,31 : 54

Claims (1)

(57) [Claims] 1. A thermoplastic plastic sheet 3 is arranged on an upper surface of a mold 2 having a hemispherical concave surface 1 on the upper surface, and a peripheral portion of the sheet is fixed to the upper surface of the mold in a sealed state. An apparatus for thermoforming a plastic sheet into a hemispherical shape by heating the sheet 3 from above with a heater 4 and bringing the interior 3 of the hemispherical concave surface of the mold 2 into a reduced pressure state so that the sheet 3 is in close contact with the hemispherical concave surface 1 Wherein a plurality of nets having different diameters are provided between the central portion of the sheet 3 and the central portion of the heater 4 so as to be overlapped with their centers aligned, and a plastic sheet is thermoformed into a hemispherical shape. Equipment to do.