Australian Wool Textile Research (continued)

CSIRO researchers,[51] recognizing the requirements outlined above for the structure for such a yarn, undertook a study of the mechanisms needed to impart individual strand-twist while concurrently folding two strands together. Feeding two, separated strands together on to one spindle, they showed that, if the twist equilibrium at the point at which the two strands converge is disturbed, it is possible to trap small amounts of alternating twist in each of the strands while the strands are twisted together. This produces in one operation a yarn with some characteristics of a single yarn but one in which surface fibres are adequately trapped to withstand the abrasive forces on a weaving machine.

At first, very simple mechanisms were developed to cause this disturbance, but practical work in industry in collaboration with the International Wool Secretariat (I.W.S.) showed that even this was unnecessary, and that, provided that the spacing between the rovings was optimised,[52] a structure with sufficient fibre entrapment for weaving could be produced.

In applying this important breakthrough in knowledge to commercial spinning, there was another difficult practical problem to solve. In spinning two strands together, if one strand breaks, or the supply material for one strand runs out, the remaining strand can continue to run by itself. This produces a section of yarn that is thinner than the rest, is difficult to detect automatically, and, if allowed to reach the fabric, produces a fault that is expensive to repair. The problem was overcome by the development of a simple device that automatically detects the breaking of one strand and then instantaneously breaks out the remaining strand. The mechanism of the breakout device (Fig. 24) relies on blockage of the twist rising up the yarn from the spindle. This reduces the cohesion of the fibres, and the forming yarn breaks.

24 The first illustration (a) shows the device in its normal spinning position, with the yarn being produced passing between the protruding fingers. The section containing the fingers is pivoted and sits in a slight well. When one strand breaks, the movement of the second strand to the site as it realigns with the spindle topples the 'fingered section' out of the well and over (b), so that the single strand remaining then has to pass through a zig0zag path around the fingers, as shown in the bottom illustration. This quickly prevents twist from rising up the strand from the spindle, cohesion between the fibres is reduced drastically, and the strand breaks out.

Australian Academy of Technological Sciences and Engineering