Patent ID: 6902639

Claim:
A method of forming a seam at overlapped first and second longitudinal edge portions of plastic film comprising the steps of providing an applicator roll, a dispensing valve with a dispensing tip spaced closely to the circumferential surface of the applicator roll, two nip rolls downstream of the applicator roll, and at least one web of plastic film; moving the film longitudinally over the rotating applicator roll and then between the rotating nip rolls; dispensing, through the valve and tip, a round, continuous bead of a solvent-based adhesive, and laying that bead onto the first edge portion of the film while the film is supported by the applicator roll; dissolving into the adhesive, while the film is moving between the applicator roll and the nip rolls, part of the first edge portion of the film so as to form therein a longitudinal channel having a generally semicircular cross-section; overlapping the second edge portion onto the first edge portion, with the bead of adhesive between the two overlapped edge portions; squeezing the overlapped edge portions between the nip rolls, whereby the adhesive exudes laterally outward from the channel and is distributed smoothly between the overlapped edge portions, until the adhesive and dissolved film form a uniform band having a rounded hat-shaped cross-sectional profile.