Bag making apparatus with automatic compensation system

Abstract

A machine for making plastic bags from plastic film utilizes a rotatable drum having an adjustable diameter. The drum is constructed of a plurality of slats and includes a gear mechanism adapted for infinite variation of the drum diameter between a first smaller diameter and second larger diameter. A sealing blanket is provided for the drum and is automatically adjusted for different drum diameters to provide proper tension of the film as it passes around the expandable drum. The gear mechanism is operated manually or automatically by a motor mounted in the drum and can alter the drum diameter while the machine is running. A chill roll, a rotary handle hole punching unit, a perforator/cutter station and phase variators are also included. When the machine is used to make bags having printed material thereon, a comparator unit may also be used. The comparator unit uses an electric eye adjacent the drum to determine the spacing between activated sealing bars and an optical reader to determine the spacing between printing on the film. A mocroprocessor system compares these measured spacings to a preselected spacing interval. The microprocessor system activates the drum motor to adjust the spacing between heat seals and printed matter on the bag. The machine checks spacing on an ongoing basis to maintain proper spacing.