Patent GB-1233677-A (GB)
IPC: D02G3/26
Filed: 1969-07-29
Abstract: 1,233,677. Alternate twist yarns. E.I. DU PONT DE NEMOURS & CO. 29 July, 1969 [30 July, 1968], No. 38056/69. Headings D1F and D1W. The method for making alternate-twist plied yarns which involves false-twisting in opposite directions at least one of a plurality of parallel, "separated, running strands so as to produce alternating zones of opposite twist along the length of the strand or strands, separated by nodes of zero twist, converging and snubbing the strands downstream of the false-twisting point, and permitting the strands to partially untwist and ply about one another, is characterised by converging the strands without snubbing, immediately downstream of the twisting point, and snubbing at a point downstream of the twisting point at a distance less than the distance between nodes, and the snubbing point also being downstream of the convergence point a distance greater than ¢ the distance between nodes, plying thus occurring in the zone between the convergence point and snubbing point as a node produced at - the, twisting point upon the reversal of the direction of twist, moves through the plying zone. Referring to the Figures, strands 10 are fed through nip rolls 12 to a false-twisting device 14, then to a converging guide 20, a snubbing point provided by nip rolls 22 and then to take-up means. The false-twisting device 14 produces an S-twist in the strands 10 upstream of the device 14 and a Z-.twist downstream. The strands converge at a point 24 in the plying zone between the guide 20 and snubbing point 22. The converged strands do not ply at this stage because the twisting action of the device 14 prevents untwisting of the strands and also because there is no node, or zerotwist point, in the zone between the convergence point 20 and the nip rolls 22, which can rotate. Downstream of the point 24 is a section of previously plied yarn 18 having a node N1 and S- and Z-twist sections. When the direction of twist of the strands 10 is reversed, the nodes produced in the strands pass through the twisting device 14 and travel downstream. The strands in the plying zone are now free to untwist and rotate at the nodes, and plying begins when the nodes in the strands reach the converging means 20. A node N2 is produced in the plied yarn and twisting on either side thereof. As twisting of the strands continues in the opposite direction, Z-twist is produced in the strand upstream of the device 14 and S-twist downstream. The node N2 moves through the plying zone, and plying downstream of the convergence point 20 is prevented up to point 24' by the twisting action of the device 14. This procedure is repeated during the alternate twisting of the strands. In a preferred embodiment, air-jet falsetwisters are used, and all strands are falsetwisted in phase, the strands are converged in phase and the direction of twist is reversed at equal intervals whereby nodes in the plied yarn correspond to nodes in the strands, and the interval between nodes is constant. The strands may be constrained in the plying zone to slow down, but not prevent, untwisting and plying of the strands. In a preferred embodiment, the rate of reversal of twist is such that a node interval is produced greater than 30 inches. In a specific example, crimped nylon yarns are twisted and plied as described above.