Bag making apparatus with automatic compensation system

A machine for making plastic bags from plastic film having a repeated design thereon, said film including a reference mark corresponding to each of said designs, said film moving along a path, said machine including:

• cylindrical sealing means along said path for periodically placing a transverse seal in said film, each of said seals corresponding to one of said marks, means for driving said sealing means, and processing means for comparing the spacing between each of said marks and said corresponding seals and adjusting the diameter of said sealing means so that the spacing between said marks and said corresponding seals are at a preselected spacing interval, said sealing means comprising a cylindrical drum including:
• an axis;
• a plurality of side members parallel to said axis and including at least one sealing bar;
• first and second ends comprising means for simultaneously altering the radially position of said side members while maintaining the parallel orientation of said side members to said axis;
• motor means for driving said altering means;
• said altering means including a first set of rods extending radially outwardly from said axis of said drum at the first end of said drum, and a second set of rods extending radially outwardly from said axis of said drum at a second end of said drum, said first and second sets of rods being connected by gear means comprising a mitre gear at the inner end of each of said rods, the mitre gears of said first set of rods engaging a first ring gear mounted in surrounding orientation to the axis of said drum, the mitre gears of said second set of rods engaging a second ring gear mounted in surrounding orientation to the axis of said drum, said first and second sets of rods engaging a second ring gear mounted in surrounding orientation to the axis of said drum, said first and second sets of rods being operatively connected by said motor means, said motor means being a bidirectional motor mounted along said axis of said drum, said motor being operatively connected to said first set of rods by a first chain, said motor being operatively connected to said second set of rods by a second chain, so that when said motor is run in one direction the diameter of said drum decreases towards a first size and when said motor is run in the other direction, the diameter of said drum increases towards a second size.

A machine for making plastic bags from plastic film having a repeated design thereon, including a reference mark corresponding to each of said designs moving along a path, said machine including:

• sealing means along said path for periodically placing a transverse seal in said film, each one of said seals corresponding to one of said marks;
• means for driving said sealing means;
• blanket means surrounding a portion of said sealing means;
• means for driving said blanket means;
• means for cutting and perforating said film transversely to form separable interconnected bags;
• and
• control means for comparing the spacing between each of said marks and said seals and adjusting the diameter of said sealing means so that the spacing between said marks and said seals is consistent at a preselected spacing interval;
• and
• said sealing means includes a cylindrical drum comprising:
• an axis;
• a plurality of side members parallel to said axis which include a plurality of slats and a plurality of sealing bars;
• and
• an adjusting means including a first set of rods extending radially outwardly from the axis of said drum at the first end of said drum to said side members and a second set of rods extending radially outwardly from said axis of said drum to said side members at the second end of said drum, said first and second sets of rods being connected by gear means comprising a mitre gear at the inner end of each of said rods, the mitre gears of said first set of rods engaging a first ring gear mounted in surrounding orientation to the axis of said drum, said first and second sets of rods being operatively connected by motor means including a bidirectional motor mounted along said axis of said drum, said motor being operatively connected to said first set of rods by a first chain, said motor means being operatively connected to said second set of rods by a second chain, so that when said motor is run in one direction the diameter of said drum decreases towards said first size and when said motor is run in the other direction the diameter of a drum increases toward a second size.