Continuous reciprocating web drive means working with intermittent heat seal forming means

Claim 1

In a heat sealing machine operable on continuous plastic web, the machine including a pair of spaced shuttle rolls reciprocally movable in unison adjacent to a pair of more closely spaced idler rolls, said pairs of rolls adapted to have plastic web threaded thereabout, a drive means arranged to drive said shuttle rolls reciprocally to temporarily stop the plastic film, and a heat die for forming a heat seal in the stopped web located downstream, relative to the direction of normal web movement, of one of said shuttle rolls and wherein an endless timing belt is threaded abouT said pairs of rolls, and a single direction clutch is engaged with said belt, adapted to prevent said belt between said shuttle rolls and the portion of said film at said heat seal die from moving during the forming of the heat seal as said shuttle is driven in the take-up direction, the improvement wherein said single direction clutch is combined with a drive means for selectively rotating the normally stationary part of the clutch, said drive means energizable after a heat seal formation is made to cause movement of said endless belt and simultaneous movement of said film at said heat seal die away from said heat seal die despite continued normal web stopping movement of the shuttle and endless belt threaded thereabout against the single direction clutch.