SUPPLY CONTROL ROTATING STRETCH WRAPPING APPARATUS AND PROCESS

摘要

A rotatable film wrapping apparatus for wrapping a load on a conveyor with an overwrap of stretched plastic film web, having a ring-mounted film web pre-stretch mechanism which stretches and dispenses film at a varying speed controlled independently of variations in film tension and speed between the pre-stretch mechanism and the load, and a supply speed control mechanism which varies the supply speed of web from the pre-stretch mechanism as the ring rotates. The supply speed control mechanism is configured as a predetermined model of the load to minimize variation in film elongation and containment as successive load edges intercept film web during wrapping, thereby locking in these characteristics at predetermined levels for film web wrapped across the load side which ends at the edge. Because the supply speed control mechanism drives the pre-stretch mechanism independently of the moving film web, tension reductions in the web caused by holes at web imperfections do not slow or stop the pre-stretch mechanism, so that holes move to the load without expansion and web destruction. The supply speed control mechanism overcomes rotational inertia of the film roll and pre-stretch mechanism to accelerate and decelerate film supply without delay caused by inertia.