SHEAR PIN BREAK DETECTING DEVICE

PURPOSE:To efficiently detect a shear pin break by mounting a sensor, having a crystal vibrator whose resonance frequency is prevented from easily changing by a temperature, to a rotary shaft. CONSTITUTION:A sensor 2 has a crystal vibrator, and this crystal vibrator is oscillated by a signal from a control coil 3. The control coil 3 feeds the signal to the sensor 2 and also receiving a signal from the sensor 2 to be transmitted to a processor 4. In the processor 4, a process of generation or the like of an alarm is performed by whether the signal from the sensor 2 is provided or not. Since the sensor 2 constitutes a loop circuit with a lead wire 7 partly inserted into a detecting shear pin 1, when the lead wire 7 is cut off by breaking the detecting shear pin 1, the vibrator is not oscillated. The crystal vibrator has a resonance frequency, and when this frequency is oscillated from a processor side, induction action is generated. At the time of receiving action in the processor side, only an echo wave is caught, and when this echo wave disappears, abnormality is judged to generate an alarm signal from the processor 4.