Abstract: An apparatus for fabricating a flexible cylinder from multi-ply flexible web material has a cylindrical forming cavity with a longitudinal opening through which the flexible web material is fed into the cavity. A non-metallic cylindrical mandrel, about which the flexible web material is fed, is mounted along the central axis of the cavity. The diameter of the mandrel is less than the diameter of the cavity in which it is disposed by an amount greater than the thickness of the web material. The web material is fed loosely around the mandrel by a feed roller to form a flexible cylinder having an internal diameter greater than the diameter of the mandrel and an outer diameter less than the internal diameter of the cavity. The amount of web material fed is enough to form a narrow longitudinal overlap zone which is heat sealed to form a longitudinal seal.A seam presser holds the overlap seam during sealing and subsequent cooling.

Abstract: Three-ply web material is rolled approximately 360.degree. into the form of a cylinder within a preform cavity. A feed roller at the opening rotates continuously and a spring loaded pressure plate has an edge at the opening which forces the web material against the feed roller. After the trailing edge of the segment of web material has passed the edge of the pressure plate, contact between feed roller and web material is lost and the circumferential position of the seam of the preform is thus precisely located. There is a slight overlap between the ends of the material at the same. The preform is longitudinally transferred into a non-conducting cylindrical forming cavity where heat and pressure are applied to fuse the overlap and form the seam. Heat is applied by induction heating through the walls of the forming cavity to the aluminum ply at only the overlap area. Pressure is applied by an expandable balloon mandrel inside the preform.