METODO PER LA PRODUZIONE DI TUBI AVVOLTI ELICOIDALMENTE E TUBI PRODOTTI CON TALE METODO

摘要

A typical embodiment of the invention produces helically wound tubes from strips of thin plate in which adjacent edges are provided with interlocking ribs that are folded over to form a compressed bead. A further rib is formed at the bead, the bead providing one of the sides of the new-formed rib.