9—THE INFLUENCE OF THE UNDER-PRESSURE IN THE ROTOR ON THE PROPERTIES OF OPEN-END-SPUN COTTON YARNS AT DIFFERENT VALUES OF THE ROTOR SPEED AND OPENING-ROLLER SPEED

An investigation of the influence on yarn properties of the under-pressure produced in the rotor in spinning cotton yarns of from 18 to 50 tex is reported. It is shown that, for rotor speeds of from 38 000 to 72 000 r/min, under-pressure influences both yarn irregularity and the number of imperfections in the yarn and does not significantly affect tenacity and elongation at break. In the experimental range considered here, the existence of optimum values for under-pressure is shown. These are between 600 and 700 mm of mercury. Optimum values for opening-roller speed were from 6000 to 6500 r/min. These figures are close to conditions recommended by the machine makers.