Patent ID: 7506491

Claim:
A machine for packaging food products in trays which are sealed at the top with thermoplastic film, said machine comprising: a reel and film feeding means for controlled unwinding therefrom of film for closing the trays, the reel of film arranged with a horizontal axis thereby allowing the film to be unwound from the reel; first deviating means situated below the reel and around which the film is deviated for changing a path of the film from a descending path to a horizontal path, the first deviating means comprising a fixed guide curved at the bottom and one or more rollers; second deviating means for altering a path of the film; rollers mounted on a vertically movable structure supporting a punching head on one end and fixed to a take-up beam supported rotatably in a projecting manner by a lug of a fixed frame of the machine on another end, the rollers being actuated by a roller motor, the roller motor, together with a film feeding motor, are actuated with constant control of torque wherein the film can be first stretched above the tray to be closed and then the film feeding motor can perform a small backward cyclical movement in order to limit the longitudinal waste of the film which during this step is also kept suitably stretched; counter-die means for supporting at least one tray horizontally, along an upper edge, with a predefined orientation and for displacing it horizontally underneath a horizontal section of film; welding means situated downstream of the first deviating means for welding the film sealingly onto an upper edge of the tray; means situated upstream of the first deviating means for blowing an appropriate quantity of modified atmosphere at appropriate pressure values into an open part of the tray which advances underneath the film until the tray has been completely sealed by the film; separating means for separating from the film, a portion of the film welded to the upper edge of each tray; collecting means for taking up the waste film produced by the separation means, the collecting means operating in conjunction with the film feeding means, whereby at least the section of film on the horizontal path advances continuously stretched both longitudinally and transversely; positioning means which at a start of a cycle supply and position correctly the trays to be closed in the counter-die means; lifting means which at an end of the cycle, raise the closed trays from the counter-die means; tray conveying means for conveying away the closed trays; and means for horizontally moving the counter-die means, which at the end of the cycle are adapted to bring the counter-die means back into a starting position for repetition of a new working cycle.