Patent GB-1288915-A (GB)
IPC: D06H3/08
Filed: 1969-11-28
Abstract: 1288915 Detecting faults photo-electrically APPALACHIAN ELECTRONIC INSTRUMENTS Inc 28 Nov 1969 [13 Dec 1968] 58263/69 Heading G1A [Also in Division G4] Apparatus for detecting slub-like defects in yarns forming a yarn sheet comprises a light source and detector mounted at the respective edges of the sheet so that the detector responds to variations in the intensity of the beam and a control circuit for producing an output signal responsive to a defect and arranged to indicate the number or numbers per unit length of defects. Yarns from a reed pass through eye board 28 under hold down bar 29 through reed 30 and are passed as a sheet over a guide 16 to be in alignment with the optical axis of a collimated light beam between source 17 and detector 23. The yarn sheet passes over measuring roll 31 to drive generator 34 and is wound on beam 11 of the beamer. Attached to the frame of the apparatus are amplifier 32 and relay 33 housings. The circuit shown in Fig. 3 comprises three channels 36, 37, 38 for investigating major defects, minor defects and the number of defects as a function of length respectively. A signal proportional to the size of the defect is produced by detector 23 and applied to each channel which include an operational feedback amplifier 36A, 37A, 38A and a comparator 36B, 37B, 38B. The defects channels are similar and the signal from detector 23 is taken through selectable capacitors 36C1, which determine the lower response level, to amplifier 36A whose gain is determined by the setting of resistor 36R3; the resistor being calibrated directly in defect size. A reference voltage of -1 volt is provided by voltage divider 36R9, 36R10 so that the comparator output switches from +10 volts to -10 volts when the output from amplifier 36A exceeds reference voltage. The comparator is provided with positive feedback to improve its switching action. The negative output of the comparator supplies a monostable circuit 36D which produces a pulse of 50ms duration to actuate an electro-mechanical counter through amplifier 36E. If switch 40sw is made, the pulse will pass through OR gate 41 to operate relay RE1 and thereby stop the beamer. The only difference between the defects channels 36, 37 is in the setting of the feedback resistors to give greater sensitivity for channel 37 so that all defects are detected. In addition the output of channel 37 is not normally used to stop the beamer. Channel 38 is used to measure the number of defects in a unit length by feeding the output of comparator 38B into counter circuits 43, 44. Circuit 43 measures the length of yarn sheet by counting the pulses generated from generator 34 and provides control pulses for resetting and operating counter 44. The length of yarn run between resetting pulses can be altered by a switch in circuit 43. If the allowable number of defects set by a switch in circuit 44 is exceeded a pulse is obtained from monostable circuit 38D to operate counter 38F and if required to stop the beamer. If the set number is not exceeded the counters are reset at the end of the set yarn length. This feature of the operation of the apparatus forms the invention claimed in Specification 1288916.