DETECTOR FOR SEAM, HOLE OR THE LIKE IN CLOTH SEAM OR THE LIKE HOLE IN CLOTH

摘要

PURPOSE:To detect a seam accurately by arranging a receiving section which receives an ultrasonic wave passing through a cloth to output a signal according to a magnitude thereof and an AGC amplifier which amplifies an output of the receiving section to correct a difference in thickness of the cloth. CONSTITUTION:A pulse-like ultrasonic wave being transmitted from a transmitter 2 is received with a receiver 6 passing through cloths 3 and 4. An output signal from the receiver 6 is outputted through a band pass filter 7. Whether the cloth is thick or thin, any output is made almost constant to correct a difference attributed to the thickness of the cloth with an AGC amplifier 12 automatically. For example, when the ultrasonic wave passes through a seam, transmission thereof increases and hence, an output of a dual wave detecting section 9 becomes higher as reaction signal. This change is compared with a reference voltage of a comparator 13 and as it is higher than the reference voltage, the comparator 13 outputs a signal of an H level thereby conveying the passage of the seam to a reaction signal processing section 15.