Abstract: Self-twist plural yarn strands are produced by a system wherein at least two singles yarn strands are individually twisted to form twisted strands each having longitudinally spaced nodes, and strands are brought together in a parallel relationship with the nodes of one strand substantially aligned with the nodes of each other strand. The corresponding nodes from one strand are fastened to those of each other strand, and the strands are allowed to ply. The node fastening means comprises a rotating member having a contact surface for fastening the nodes by gathering and twisting of the fibers from one strand with those of another strand at the nodes of each respective strand. Ply yarn twist uniformity is assured through the use of improved twist insertion jets, together with a means for holding singles yarns separate to allow longitudinal levelling of singles yarn torque prior to plying.

Abstract: Thermoplastic yarn ends are spliced by overlapping side-by-side and spinning with an air jet circumferentially around a longitudinal axis of a cylindrical cavity with sufficient initial slack to insure engagement with the wall of said cavity. Heat is generated by the spinning action and concentrated in high twist nodal points giving rise to plasticization of the yarn and bonding of adjacent fibers. The spinning device has gripping elements for securing the yarn ends and introducing the necessary predetermined slack.