Abstract
The geometrical effects of an air suction gun on yarn motion were clarified by measuring postures of a running yarn with a still camera in order to promote the suction performance by controlling the yarn motion appropriately. The relation between the yarn posture and yarn suction force was also discussed. The yarn posture is a helix. This helical motion greatly improves the suction efficiency of the air suction gun owing to high concentration of air drag on the yarn. Helix diameter of yarn posture dy and helix pitch of yarn posture py decrease with an increase in the compressed-air inflow angle and a decrease in the throat diameter of de Laval tube, and are almost independent of the passage diverging angle of nozzle and the converging angle of de Laval tube. Unfavorable values of the geometrical parameters cause large fluctuations in yarn postures, i.e. violent yarn motion. A stable yarn posture with appropriately small dy decreases the friction between the yarn and the wall of tube, and an appropriately small py increases the contact area between the yarn and the air. Hence the yarn suction force is promoted.
