With the aim to clarify a generation mechanism of interlaced yarn, the yarn motion in a slit-type interlacer was analyzed by high-speed video images. Results obtained are as follows: (1) The running yarn in a closed state receives air jets and turns into a dispersion state where filaments separate from each other. With progress in time, the filaments reach the slit height and vicinity of the two air jet nozzles. Then, twin vortex from the two air jet nozzles produces relative motions of the dispersed filaments and/or filament groups at the yarn cross-section in the direction of the yarn axis, resulting in the twisting state of filaments. An opening part is composed of the dispersed filaments in this state and tangling parts are composed of entanglements accumulated at both ends of the opening part. The iteration of these three states (closed, dispersion and twisting) produces interlaced yarn. (2) It took the shortest time and yarn length to form the dispersion state, whereas the twisting state took the longest, and hence, opening parts are longer than tangling parts. (3) The yarn in a closed state showed circular motion along the air vortex at the yarn passage crosssection located at the two air jet nozzles. (4) The positions, where the dispersion state begins, were made clear.
