| 摘要 |
An improved method and apparatus for shaping sheets of thermoplastic material is disclosed in which sheets are pressure molded against a mold member by the direct application of a liquid coolant under pressure thereto. The coolant contacts the surface of the sheet and upon pressure reduction vaporizes and accordingly, due to the heat of vaporization effect, rapidly absorbs a large amount of heat from the sheet so as to form a solidified skin on the outer surface of the sheet after or simultaneously with the shaping of said sheet. The sheet thus remains in the mold for a shorter dwell time inasmuch as the sheet becomes more quickly shape retentive because of the rapid cooling. This accordingly permits smaller and less bulky equipment to be utilized in sheet shaping processes. The attendant reduction in equipment size can result in substantial cost savings for such equipment.
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