Improvements in or relating to the production of crimpable non-torque yarn and to yarn so produced

807.516. Crimping yarn. BRITISH NYLON SPINNERS Ltd. Oct. 8, 1956 [Oct. 11,1955], No. 28864/55. Class 120(3) " Non-torque " yarn consisting of a filament or filaments of thermoplastic material, e.g. polyamide, polyester or cellulose triacetate, which may be relaxed to induce crimp therein, is produced by subjecting a yarn to the successive treatments of highly twisting, e.g. 75 turns per inch, in one direction (relative to any datum twist. e.g. 0-¢ turns per inch), heat-setting (with or without the presence of moisture), cooling as by passage through an air gap, reverse twisting in one or more stages to " high twist of effective equal magnitude (measured from the datum twist) to the initial high twist but in the opposite sense thereto ", i.e. a twist imparting an equivalent torque to the yarn when such twist is subsequently set, heat-setting (with or without the presence of moisture) at a temperature equal to or lower than that of the first setting treatment, cooling and detwisting to the datum twist. The high twisting and detwisting may be effected in stages or continuously by means of successive and contra-rotating false-twist devices. Heat-setting may be effected by means of pressure steam, infra-red heating tube(s) through which yarn passes without making physical contact, or contact of successive runs of the yarn with one or more curved heated plates. Specifications 786,420, 788,944, 797,051, 797,659 and 801,464 are referred to