Device for varying the opening between the welding element and the counter-welding element in packaging machines

A welding device for a packaging machine which packages products arranged in sequence on a conveyor belt in a continuous tubular plastic film, the device comprising:

• a car supported for horizontal reciprocation parallel to a running direction of the conveyor belt;
• a welding unit including a main welding element and a counter welding element supported by said car and positioned on opposite sides of the tubular plastic film, said welding elements being vertically moveable relative to each other between a rest position in which said welding elements are spaced apart and an engagement position in which said welding elements engage for welding and cutting the tubular plastic film interposed between said welding elements;
• drive means, supplying a predetermined constant angle oscillatory motion, for powering vertical reciprocation of said welding elements between said rest and engagement positions;
• and
• first adjustment control means and second adjustment control means, between said welding unit and said drives means, for varying distances traveled by said welding elements between said rest position and said engagement position for different package heights, said adjustment control means including adjustable crank means, said crank means being operatively and rotatably linked with said drive means on one side thereof and said welding elements on an opposite side thereof.