Fiber feeding onto the yarn tail in friction spinning Part I: Flow pattern in the fiber transport channel and fiber landing on the yarn tail

Air and fiber flow patterns and fiber landings are two important parameters we discuss in this paper. We use tracer filaments to study the effect of various parameters such as combing roller rotation, friction roller rotation, and suction air pressure on the fiber flow pattern in the transport channel. We also use staple fibers to consider the mechanisms of fiber landing and the manner of fiber capture by the yam tail. Our results show that although the rotation of combing and friction rollers affects the flow in the channel, the most important parameter is suction air pressure. One of the most important results is the small size of the flow outlet, about 25 mm when the main parts of the machine are running, while the outlet of a conventional channel is 115 mm. This means that most of the fiber supply may land on the yam tail at the flow outlet of the channel. Although considering fiber motion within the transport channel is a difficult problem, the body of the flow is found by tracing the shape of a filament in the channel. The results of fiber landing experiments show that there are two kinds of landings: "drawing" by the yam tail and the fiber "trapping" by itself on the yam tail surface. The landing and capturing phenomena depend on the fiber position in the transport channel and the yam-forming zone. Both drawing by the yam tail and the fiber trapping by itself may occur as the fibers pass through the transport channel. Most of the fibers fed from the upside of the transport channel will be drawn by the yam tail, while the probability of both drawing and trapping is almost equal for fibers fed from the downside of the channel.