11—THE EFFECT OF BACKDRAFT APPLIED AT THE FIRST GILLING OPERATION AFTER WORSTED CARDING

The application of backdraft at the first gilling operation after carding results in significant reduction in percentage noil and an increase in the mean fibre length of the top. These effects depend on the backdraft and direction of feed. Percentage noil is also dependent on backratch but is independent of the faller-bar pinning density. Measurements are also given to show how back-roller force is affected by backdraft, backratch, and the total free space between the pins and the fallers.     

Purpose-grown Wools

An account is given of an investigation of the dimensional changes in eyelet structures made from cotton, Vincel. and Courtelle yarns at three states of relaxation, namely, dry relaxation, wet relaxation, and washing. Observations revealed that the Courtelle structure exhibited a collapse in the configuration of the eyelet stitch when the fabrics were removed from the machine. It is suggested that this collapse could have been due to elastic recovery of the transferred yarn after stitch formation and to the presence of insufficient cohesion forces between the yarns within the structure.

Measurements of eyelet courses/in, (e _c), eyelet wales/in, (e _w), and eyelet density (E) showed that, in both the dry- and the wet-relaxed states, the fabrics exhibited a certain amount of distortion. It was concluded that the incomplete relaxation of the fabrics in these states was largely due to obstructional effects of the transferred loops. The agitation action of the washing treatment brought about a considerable rearrangement in the structure. This was particularly noticeable for the Vincel fabrics, whose geometrical parameters were readily represented by equations similar in form to those of the plain structure. The dimensional changes in length, width, and area due to washing showed an increase in the lengthwise shrinkage with the increase in loop length. Fabric-width shrinkage exhibited considerable change and reached maximum values of 42% and 26% for the cotton and Vincel fabrics, respectively, at greater loop lengths. Changes in area showed a decrease in the percentage shrinkage with the increase in loop length.     

18—OSCILLATING ROLLERS FOR SELF-TWIST SPINNING

A method is described for making self-twist yarns by using rollers that simultaneously rotate and oscillate. The technique provides a substantial improvement over previously known methods. The twisting action of sinusoidally oscillating rollers is examined theoretically and comparison made with twist levels observed experimentally. The resultant understanding enables machine parameters to be selected to give desired twist-cycle-length characteristics in in-phase self-twist yarns.