Abstract: A preheater assembly for softening a selected portion of plastic stock material prior to severing and edge sealing is disclosed. The preheater assembly includes a pair of opposed preheaters, each having a heater tip connected to a source of heated air. The air flows through the tip to maintain it at a preselected temperature. The preheaters are mounted on opposite sides of the stock material for motion toward the material to engage it on opposite sides to heat and soften it, and away from the material to release it. Clamp elements engage the stock material during the heating and softening process.

Abstract: A method of and apparatus for manufacturing stock material from which bags or other containers may be formed is disclosed. A folded plastic film is fed from a stock roll onto a plurality of carrier rollers which support the film in a horizontal position. Simultaneously, a separate closure strip is fed from a second stock roll through a guide block which aligns the strip with a sealing station, the two halves of the closure strip being pressed together to maintain proper alignment. The upper ply of the folded plastic film is fed into the heat sealing apparatus at the sealing station, the edge of the upper ply being aligned with one edge of the closure, and the film and the closure strip are fed continuously through the sealing station where they are welded together. The lower ply of the film web is folded downwardly so that it bypasses the sealing station.

Abstract: A plastic container is provided with a plastic bead seal at the junction of the interlocking fastener and the side edges of the container. The plastic bead seal acts as a barrier to the passage of fluids or contaminating bacteria through the fastener at this junction. A method and apparatus are provided for flowing plastic under heat and pressure into and across the junction to form the bead seal barrier.