| 摘要 |
PROBLEM TO BE SOLVED: To control the draw down of sheets at heating by a method wherein an air permeable heat-resistant supporting member is spanned between both the sheets parallel to each other so as to carry out the subsequent forming operation under the condition that the above-mentioned spanned state is retained. SOLUTION: When thermoplastic synthetic resin sheets 1 and 2 are pinched by clampers 4a and 4b and supported parallel and horizontally, one layer of air permeable heat-resistant supporting member 6 parallel to both the sheets 1 and 2 is simultaneously spanned. The spanned position of the air permeable heat-resistant supporting member 6 is normally between an upside sheet 1 and a spacer 3. Next, both the sheets 1 and 2 are softened by heating from above and below with heaters 7a and 7b. At this time, though both the sheets 1 and 2 tend to sag with the rise of temperature, the drawdown of the upside sheet 1 is suppressed, since the upside sheet 1 is supported by the air permeable heat-resistant supporting member 6. Further, the sagging of the downside sheet 2 is suppressed together with that of the upside sheet 1 by balancing the pressure in a closed space 5 with the atmospheric pressure. |
