Method and apparatus for producing valve bags

摘要

The present invention relates to a method and apparatus for folding and sealing a web of material to form an item with a contoured seal such as a valve bag. Folding apparatus form the web of film into a continuous tubular web having upper and lower sections, a closed side and an open side. The open side has two folded flaps that extend into an inside area of the tubular web. A longitudinal sealer includes a floating sealer located inside the tubular web. The floating sealer and its contoured heating element are selectively and intermittently pressed against the overlapping flaps to form a contoured seal that bonds the flaps together. The contoured seal defines a self-sealing valve port through which product is poured to fill the bag. Pairs of repelling magnets biasingly elevate the floating sealer above the overlapping flaps when the longitudinal sealer is in its release position. The sealer "floats" inside the continuous tubular web so that the web can be intermittently drawn past the floating sealer with a minimal amount of drag.