| 摘要 |
When the opposing housings (1, 8) of the apparatus are closed, they form between them a small main chamber (P) delimited above by the film (H) for covering the tray and below by the tray (V) itself containing the product (M), and laterally by any suitable mechanical interface structure which surrounds the perimeter of said film and connects it to the perimeter of the upper edge (B) of the tray, this interface structure having holes (22) which are suitably distributed, are located outside the perimeter of the tray, and communicate with said main chamber (P). One or more of these holes (22) open(s) on at least one side of the tray and is/are connected to a first circuit (23, 24), while another one or more of said holes (22') open(s) on at least one opposing side of the tray and is/are connected to a second circuit (17) which in turn is connected to the inner chambers of the two housings (1, 8). Means (18, 19, 20) are provided to operate in such a way that, in the step of vacuum formation, both said first circuit (24) and said second circuit (17) are connected to vacuum forming means (21) which are kept active for a sufficient time to eliminate some of the air from the inside of the tray and to act in such a way that said first circuit (24) is connected in the next step or at the correct time to means (25) for supplying the process gases, while said second circuit (17) is closed or remains in communication with the vacuum means (21) to ensure that the process gas entering the tray from said first circuit (22, 24) causes the residual air in the tray to flow out from and/or towards said second circuit (22', 17), thus flushing and saturating the inner volume of the tray, which is subsequently sealed using known steps and means for welding and finally cutting the film (H). |
