for feeding a pressurized gas is connected in fig3 the air paths 15 and 16 are separated by spacer 14 by an interval of 0 3 to 1 mm preferably 0 4 to 0 6 mm and the angles u03b8 1 u03b8 theta and u03b8 2 u03b8 theta to the yarn path 18 are adjusted so as to satisfy the relation of u03b8 1 gt u03b8 2 in this case u03b8 1 is generally 30 to 70 degrees preferably 40 to 50 degrees and u03b8 2 is generally 20 to 40 degrees preferably 25 to 35 degrees these air paths 15 and 16 are turned in the downstream courses so as to have spaces a and b in parallel to the yarn path 18 the space a is generally 0 5 mm to 3 mm preferably 0 7 to 1 5 mm and the space b is generally 1 to 5 mm preferably 1 5 to 2 5 mm the space being larger than the space a in the interior of the yarn charging means 3 moreover there is provided a nozzle regulator 17 to regulate the flowing direction and speed of air to the yarn 7 at the outlet of the air paths 15 and 16 the nozzle regulator being optionally moved back and forth by a screw 19 as explained above the.