40—A DIRECT METHOD FOR MEASURING YARN DIAMETERS AND BULK DENSITIES UNDER CONDITIONS OF THREAD FLATTENING

Abstract

With normal types of woven fabric, the assumption of a circular thread cross-section is frequently invalid owing to the considerable thread flattening which usually occurs during weaving. As a basis for studies of fabric structure, therefore, a method has been devised whereby measures of both major and minor thread diameters may be obtained from small samples of yarn, under conditions of thread tension and compression which may be controlled to produce thread flattening similar to that which occurs particularly in weaving, but also in package winding, warping, and knitting. The method consists essentially in winding the yarn in adjacent coils on to a spindle of suitable diameter, this giving a disposition of the yarn which enables direct measurements of major and minor diameters to be taken. These diameters may be applied directly to fabric geometry, or, by combining with yarn count or denier measured over the same length of yarn, may be used to calculate bulk density of the yarn and hence density of fibre packing. Results show that both these quantities may vary considerably. The method is applicable to both filament and staple yarns over a wide range of counts, and offers interesting possibilities as a new and more realistic basis for a single fabric geometry applicable to all types of woven cloths.