An Experimental Study of Fancy Yarn Formation in Rotor Spinning

Doktorsavhandling, 1993

FANCY YARN is a yarn with deliberate imperfections. Strange as it may appear, in present times when defect-free yarn is considered to be a premium product, fancy yarns, with all their imperfections, are also in demand. It is a different matter that the volume production of fancy yarn is insignificant in comparison to the normal yarn production. The demand for fancy yarns is due to the special aesthetic appeal it imparts to the fabric made using such fancy yarns. Fabrics produced using fancy yarn find applications in normal and high-fashion clothing, curtains, carpets, upholstery fabrics, as a base for "effect" wallpaper manufacture and many more. Ring spinning is successfully employed to manufacture fancy yarn. Rotor spinning, which offers economical benefits over ring spinning, has also been employed to produce fancy yarn. A number of ideas have been applied in practice to produce fancy yarn on rotor spinning machines. The approach of these conventional devices has been to control the speeds of the mechanical elements of the rotor spinning machine. Because the rotor spinning machine is a very high speed spinning machine, with the latest ones having rotor speeds of over 100 000 rpm, the conventional devices become limited in their approach, not application. A new approach is therefore necessary to produce fancy yarn on rotor spinning machines. This work is a new approach in that direction. The principal idea is to affect the fibre flow without altering the speeds of the mechanical elements of a rotor spinning machine. To bring about this influence of the fibre flow, pressurized air has been employed for the first time. The concept of using pressurized air not only offers a new alternative to produce fancy yarn on rotor spinning machines, but also offers a simple and relatively inexpensive route to fancy yarn manufacture. Hence, this approach has been referred to as pressurized air method of producing fancy yarn. The fibres flowing in the fibre transport channel of the rotor spinning box are affected by pressurized air. This influence of the flowing fibres by the pressurized air causes the effects or the imperfections in the yarn being spun to result in a fancy yarn. The duration of the time the pressurized air is applied to affect the fibre flow, influence the characteristics of the effects such as thickness, length and appearance. By programming the pressurized air blowing time, effects can be produced in a predetermined way. In this way the need to alter highly frequently the speeds of the mechanical elements of a rotor spinning machine is obviated. As with the conventional methods employed on rotor spinning machines in the production of fancy yarns, the pressurized air method also has its own limitations. While the conventional methods can only produce effect lengths longer than the rotor circumference, the pressurized air method can only produce effect length shorter than the rotor circumference. But by combining the conventional method and the pressurized air method, the shortcomings of the two methods can be overcome in a unique way. This work, being the first of its kind, provides a fairly comprehensive understanding of the concept of using pressurized air in the production of fancy yarns on rotor spinning machines.