| 摘要 |
1451662 Packaging with inert atmosphere W R GRACE & CO 3 May 1974 [7 May 1973] 21685/73 Heading B8C In a packaging apparatus successive trays of at least one row of thermoformed trays are closed by a film 10 which is guided closely above the trays as they are fed to a closure station 9 so that inert gas introduced into the or each tray at the closure station also flushes at least the next following tray in the or each row. The closure station includes sealing heads 32, 34 which heat-seal the film 10 along the leading and side edges of the or each tray at the station 9 and simultaneously heat-seal the trailing edge of the or each preceding tray. The inert gas is introduced into the trays by one or more flat pipes having an outlet adjacent the location whereat said leading edge(s) is sealed. The trays may be vacuum or pressure formed at a station 7, in a film 2 which is heated by infra-red heaters 5. A male plunger may be used to assist the thermoforming. Lower members 31, 32 at the forming and closing stations are mounted on a common beam for simultaneous vertical movement. The mould may be interchangeable to produce trays of different sizes. The covering film may be clamped by a bar 36 operative in response to a signal from a photo-cell which detects register spots on the film, to tension the film for sealing. The closed trays are severed from one another at a station 24. The tray forming film may be a laminate of polyethylene film, polyvinyl alcohol film and polyvinyl chloride film. The covering film may be a laminate of polyethylene film, aluminium and Cellophane (Registered Trade Mark) or polyester film. |
