Apparatus and method for heat-sealing a film cover to open ended

Abstract

A film cover is heat-sealed to the open end of containers and cut from a film stock by a cam-actuated, orbitally moving knife blade which severs the film stock along a circumferential region closely adjacent the container's open end. A major extent of the orbital movement of the cam-actuated knife blade about the open-ended container is preferably substantially circular (to closely conform to the circular cross-sectional geometry of open-ended containers to be film-covered). However, a minor segment of the knife blade's orbital movement is cam-actuated so as to follow a segment of an arcuate non-circular (e.g., elliptical) path to form a protruding tab on the film cover so as to allow a consumer to more easily grasp and remove the same. The film is preferably continuously supplied to the sealing and cutting zone, while the waste web (i.e., the film remaining after the film cover has been cut from the film stock) is continuously retrieved from the sealig and cutting zone at substantially constant rates. Meanwhile, discrete sections of the film stock are sequentially indexed into the momentarily stopped within the zone to allow for sealing of the film cover to the open-ended container. During such momentary stoppages, a dancer roll assembly accommodates the continuous supply and retrieval of film stock and waste web to and from the sealing and treating zone, respectively.