Abstract: An apparatus for ultrasonically detecting an edge of a web, includes a ultrasonic-wave transmitter transmitting ultrasonic-wave pulse train, a ultrasonic-wave receiver receiving the ultrasonic-wave pulse train and converting the received ultrasonic-wave pulse train into electric signals, the web being fed between the ultrasonic-wave transmitter and receiver, a rectifying circuit for rectifying the electric signals, a low-pass filter circuit for smoothing output signals transmitted from the rectifying circuit, a first sample-holding circuit for sampling an output signal transmitted from the low-pass filter circuit, at first timing, a second sample-holding circuit for sampling an output signal transmitted from the low-pass filter circuit, at second timing later than the first timing, a third sample-holding circuit for sampling an output signal transmitted from the first sample-holding circuit, at the second timing, and a differentially amplifying circuit for calculating a difference between output signals trans

Abstract: An apparatus for ultrasonically detecting an edge of a web, includes a ultrasonic-wave transmitter transmitting ultrasonic-wave pulse train, a ultrasonic-wave receiver receiving the ultrasonic-wave pulse train and converting the received ultrasonic-wave pulse train into electric signals, the web being fed between the ultrasonic-wave transmitter and receiver, a rectifying circuit for rectifying the electric signals, a low-pass filter circuit for smoothing output signals transmitted from the rectifying circuit, a first sample-holding circuit for sampling an output signal transmitted from the low-pass filter circuit, at first timing, a second sample-holding circuit for sampling an output signal transmitted from the low-pass filter circuit, at second timing later than the first timing, a third sample-holding circuit for sampling an output signal transmitted from the first sample-holding circuit, at the second timing, and a differentially amplifying circuit for calculating a difference between output signals trans

Abstract: A safety device for a gas burner comprises a first ignition nozzle 31 in a pilot burner 3, an inflammable gas guide tube 32 facing the first ignition nozzle, a second ignition nozzle 33 at the end of the guide tube oriented toward a main burner 2, a pressure sensing tube 6 coupled between the guide tube portion near the first ignition nozzle and one diaphragm chamber of a differential pressure sensing device 7, and an automatic valve 4 actuated by the pressure sensing device to close a main gas pipe 1. If the flame at the first ignition nozzle is extinguished the pressure near the beginning of the guide tube increases sharply, which actuates the pressure sensing device 7 to close the valve 4 and terminate combustion.