Wrapping machine and method with four side rotary tucker

Claim 1

In the method of packaging articles by continuously forming a strip of flat heat sealable material into a tube in which equally longitudinally spaced articles are inserted and transported by the tube, the tube defining top, bottom and side walls whose unoccupied longitudinally spaced portions are deflected toward the central axis of the tube by tucking members; the improvement in said method comprising the steps of simultaneously creasing the side walls of the tube inwardly at unoccupied portions of the tube substantially at the midplane of the tube, said creasing step leaving the creased side walls of the tube spaced by a minimum spacing at a single transverse zone, substantially concurrently deflecting the top and bottom walls of the tube into engagement at said zone along a single, narrow transverse central area that is slightly shorter than the minimum spacing between the creased side walls of the tube, bonding said top and bottom walls together along said single, narrow transverse central area when said upper and lower walls are deflected into engagement, applying longitudinally moving, frictional web feeding forces before, during and after said creasing steps to transversely opposed sides of the web side walls and the articles therein both upstream and downstream of said single bonding area with said web feeding frictional forces moving at differential speeds, the tube shortening action of said creasing and bonding steps being resisted by said frictional web feeding forces for rendering the creased portions of said tube taut at both sides of said bonded area during the creasing step, said web feeding frictional forces downstream of said bonding area accommodating longitudinal movement of the downstream article toward the upstream article during said creasing step, feeding the creased and bonded area to a position downstream of the position at which the creasing and bonding steps were performed, and transversely bonding and severing the entire width of the tube through the creased and previously bonded area between articles that have been fed to said downstream position.