| 摘要 |
Method of thermoforming plastic sheets, in which a sheet 2 is heated and gripped between the periphery of a mould 1 and a frame 3 placed so as to bear on the said periphery, the mould 1 being drilled with holes 6 emerging into a chamber 7, and a partial vacuum is created in the chamber 7 so as to press the sheet 2 up against a mould-cavity wall 1a of the mould 1 in order to thermoform it and/or a compressed gas is introduced into a bell 5 located on top of the frame 3 so as to exert, on the sheet 2, a pressure pressing it onto the mould 1, characterised in that at least a second, perforated, plastic sheet 11, 12 is placed beneath a non-perforated plastic sheet and these sheets 2, 11, 12 are pressed simultaneously onto the mould 1, these following the shape of the mould-cavity wall 1a, by creation of a partial vacuum in the said chamber and/or by application of a gas pressure in the bell 5 above the sheets 2, 11, 12. This method enables two or more plastic sheets to be simultaneously thermoformed with one conventional installation, and this is achieved with a very significant reduction in cost price. <IMAGE>
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