GB1270885A - Apparatus for the automatic adjustment of a yarn cleaner - Google Patents

Abstract

1,270,885. Adjustment of yarn cleaner sensitivity; measuring yarn thickness. SCHWEITER ENG. WORKS Ltd. Feb.23, 1970 [March 5, 1969], No.8664/70. Headings G1A and G1N. The sensitivity of a yarn cleaner device comprising a yarn measuring cell connected to an amplifier and a pulse shaper, is automatically adjusted, to compensate for variations in yarn characteristics other than that measured by the cell and in ambient conditions, by generating an average value signal from a predetermined number of signals from the pulse shaper output and using this to control the amplifier gain. In the case of a photo-electric yarn detector, variations in yarn colour, ambient light fluctuations and detector contamination are compensated; with capacitive cells, humidity and moisture changes. Influences due to the yarn being smooth or rough, twisted, or untwisted may also be dealt with. The apparatus of Fig. 2 may be adapted for actuation by the continuous running of the yarn or may be actuated in response to insertions of yarn into the detection zone, which occur after each yarn cleaning (cutting) operation. With reference to the latter case, on each insertion, switch d in the pulse shaper circuit 4 is closed for a predetermined time, capacitor 14 charging up to the amplitude of the amplifier 3 output. The voltage on capacitor 14, modified by impedance matching circuit 16, is transmitted, on subsequent momentary closure of switch e, as a pulse to threshold evaluation circuit 5 (feeding cleaner 6) and to the pulse evaluation circuitry 10, 11, 12. The above-mentioned predetermined number of signals (pulses) are counted by binary counter 11, which on reaching the predetermined count initiates a timed sequence of pulses on outputs 22, 23, 24. Pulses due to repeated yarn insertions and consequent closures of switch e are cumulatively stored in prestorage capacitor 26 until the predetermined count is attained in counter 11. Then, in accordance with the timed sequence, a pulse on 22 momentarily closes switch a, resulting in clearing of main storage capacitor 28; a pulse on 23 closes switch f, resulting in transfer of the sum voltage in capacitor 26 to main capacitor 28; and a pulse on 24 closes switch b to clear capacitor 26 and prepare for a new averaging cycle. The output from 12 (via impedance matcher 33) is applied to a control device 7 - a bridge network or thermistor - to operate on the amplifier gain. In the case in which a continuous running yarn is utilized to produce the signals for averaging, switches d and e are periodically sequentially closed under the control of a pulse transmitter. Coarse adjustment of amplifier gain in accordance with yarn quality or number is by manual precontrol 34.