| 摘要 |
<p>Between the two housings each having a recess and below and parallel to the film, there is provided a frame having openings greater in plain view than the underlying trays to be packaged, supported such that, during the closure of the housings the frame interacts with seal and contributes to the formation of a main chamber delimited by the upper edge of the tray and by the film above this edge. Air is removed from these recesses to form the desired level of vacuum therein, while, in the main chamber is isolated from the recesses of the two housings, so that the process gases can be injected directly into the main chamber, while a corresponding quantity of atmospheric air is directed into the recesses to balance the pressures on the opposite faces of the film When the process gases have been fed in, the film is welded to the edge of the tray and is cut outside this edge.</p> |
