GB754919A - Improvements in yarn and monofilament evenness testers - Google Patents

Abstract

754,919. Electric measuring systems COMMONWEALTH SCIENTIFIC & INDUSTRIAL RESEARCH ORGANIZATION. Nov. 15. 1954 [Nov. 20, 1953], No. 33071/54. Class 40(1) Irregularities in a yarn or monofilament are measured by drawing the yarn 1, Fig. 1, at constant tension past two fixed points 3, 4; maintaining the yarn between these points in transverse vibration at its natural frequency electromechanically, and measuring this frequency which varies as a function of the irregularities. The points 3, 4 are, as shown in Fig. 1, formed by pins over which the yarn is drawn, the pins 3 4 being connected to the armatures of transducers 8, 9, connected, respectively, to the output and input of an amplifier 10 arranged so that the yarn between the pins is maintained in transverse osciliation at its natural frequency, which is measured by a frequency meter 16, recorded at 17 against yarn displacement, and integrated at 19 to give an average reading of yarn count (length per unit mass). In another arrangement for maintaining the yarn in oscillation, Fig. 2, the yarn is charged to a high potential by the leading pin 23 and excited electrostatically by electrodes 24, 25, energized by the amplifier output which is fed by a transducer 9 actuated by the trailing pin 4. This arrangement may be modified by supplying the H.T. positive to one of the electrodes. The transducers may be piezoelectric, and the frequency meter may comprise a monostable multivibrator triggered once per cycle, the mean plate current of the valve which is cut-off in the stable state being proportional to the instantaneous frequency.