| 摘要 |
A process for forming a sealed package of the type comprising a rigid tray-like container having an opening at its top leading to the container interior and carrying a product such as food or the like requiring isolation from atmospheric conditions for a substantial time, the process including the steps of applying to each container a planar sheet of lid material, positioning each container in a forming chamber with the lid clamped along a peripheral line thereof, establishing a differential pressure across the lid material to stretch the material away from the container into a smoothly-curved arc as seen in crosssection, increasing the pressure above said container to force the lid material down from its arc-shaped configuration into the interior of said container and into close intimate pressure contact with the upper surface of the product.
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