| 摘要 |
Apparatus and process for stretch wrapping articles, especially heads of lettuce, wherein a roll ( 23 ) of film ( 24 ) is supported on a housing ( 21 ), and the film is supplied from the roll around a dancer roller ( 50 ) and film feed roller ( 51 ) to a pair of film feed grippers ( 33, 34 ) which grip a leading edge of the film and advance it past an opening ( 26 ), whereupon a clamp ( 27 ) engages the leading edge of the film to hold it while the grippers release and return to their home position. Additional clamps ( 28-32 ) then engage the film to hold it in place over the opening. A head of lettuce (L) is placed on the film in centered relation to the opening, and a ram ( 37 ) engages the lettuce and pushes it against the film to stretch the film through and below the opening. Gathering bars ( 38, 39 ) engage the film stretched between the opening and the head of lettuce to gather the film in a first direction, and a U-channel ( 40 ) and sealing and trimming mechanism ( 41 ) gather the film in a second direction to produce a narrow necked down section of gathered film, fuse and seal the necked down section to produce a wrapped head of lettuce, trim excess film from the lettuce, and release the wrapped head of lettuce to drop onto a take away conveyor. The film ( 24 ) is a polyethylene based multi-layer film with an outer polypropylene layer for added gloss, slip and clarity, has a 300% stretch capability, is FDA approved for direct food contact, has an anti-fog additive for moisture dissipation during temperature fluctuations, is thirteen microns thick, and has a width of sixteen inches.
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