A vacuum packaging machine for performing a vacuum sealing operation on product packages, comprises a vertical stack of vacuum chambers 4 which each manage to receive at least one unsealed product package 2 and are operable to perform an independent vacuum sealing operation on the least one product package 2. A conveyor arrangement 8, 9 is operable to load and unload a selected vacuum chamber 4 with the at least one product package, and the machine is arranged to operate the respective vacuum chambers 4 to perform the vacuum sealing operation while the conveyor arrangement is operated to load and unload another vacuum chamber 4. The conveyor arrangement loads and unloads the vacuum chambers in sequence, and the vacuum chambers are synchronously operated to perform the vacuum sealing operation to allow the conveyor arrangement to operate continuously. The conveyor arrangement comprises at least one in-feed conveyor 8 and at least one out-feed conveyor 9 which are independently movable to select the vacuum chamber to be loaded and unloaded. There may be a plurality of in-feed conveyors 8 and a plurality of out-feed conveyors 9. The vacuum chambers each have a sealing bar arranged along one side for sealing the product packages 2.
The present application is a divisional application of U.S. patent application Ser. No. 09/830,245 filed Jul. 9, 2001 now U.S. Pat. No. 7,055,297, which is a 35 USC .sctn.371 application of PCT/EP99/08131 filed Oct. 27, 1999, which claims the benefit of priority European Patent Application Serial No. 93308823.8 filed Oct. 28, 1998.
