Abstract: A method of treating filament yarn includes supplying a plurality of yarn filaments through a yarn channel of a nozzle in a yarn travel direction and introducing a blowing medium into the yarn channel substantially in a direction of the yarn travel direction and at an angle of introduction of more than about 15° and less than about 45° from a direction perpendicular to the yarn travel direction. The plurality of yarn filaments are mixed within the yarn channel so as to produce a filament yarn substantially free of knits.

Abstract: By appropriately controlling a yarn tension of an upstream side from a false twist device, variations in yarn quality among packages can be eliminated. A false twist texturing unit 7 which imparts a yarn Y with a false twist, a first feed roller 4 arranged in the upstream side from the false twist texturing unit 7, and an upstream side yarn tension control device 30 which automatically adjusts the rotation speed of a first feed roller 4 such that the upstream side yarn tension T1 is maintained within a fixed range are provided. A downstream side yarn tension control device 35 which automatically adjusts the false twist device 7 such that downstream side yarn tension T2 is maintained within a fixed range is also provided. Additionally, a determining unit 45 which determines whether or not the yarn quality is satisfactory based on the detection result of an upstream side yarn tension detecting unit 24 and a downstream side yarn tension detection unit 35 is also provided.