Safety detector for machine tols - has passive tuned circuit with coil magnetically coupled in active state to detector circuit coil

摘要

The safety device has a part which can be removed from its operating position, thus preventing the machine tool operation. The removable part has a passive tuned circuit (13) with a coil (14) which is magnetically coupled, in its operational position, to a coil (12) of an active detector circuit. The passive tuned circuit controls the oscillations of the detectors circuit. Preferably the detector properis tuned to the passive oscillation circuit frequency. Typically the detector has an amplifier (TR1, TR2) with an AC negative feedback and an AC feedback line, the coupling coil (12) being incorporated in the feedback line. Thus the feedback is boosted on connection of the coil (12) to the passive resonance circuit (13) coil (14).