| 摘要 |
PURPOSE:To obtain a safety device having extremely high reliability with respect to safety for a beam type safety device by providing a circuit for inspecting the presence or absence of abnormality in an emergency stopping circuit at the startup of a machine. CONSTITUTION:All the plural beams from a light projecting part 1 enter a photodetecting part 2 if there are no body, etc. within the dangerous zone of a press machine. Such state is detected by a synchronizing circuit 3 and the output thereof is amplified by a circuit 4, by which a transistor TR1 is conducted and a relay RL1 is energized. An emergency stopping mechanism 5 is thereby inactivated. When a switch SW is closed at the startup of the machine, the output Q of an FF circuit 7 of an inspecting circuit 6 is converted to a high and low level by the signal and the input side of the circuit 4 goes to a low level, thus making the TR1 and a photocoupler PH1 nonconductive. Since the Q goes to a high level, a photocoupler PH2 conducts but TR2 does not conduct as the TR2 is in series to the PH1. RL2 is therefore not energized and the mechanism 5 does not operate. The nonconducting time of the TR1 is determined by the time constant of the circuit 7 and since said time is set shorter than the time required for opening and closing of the RL1, the RL1 and the machanism 5 do not operate unless there is the abnormality to make the TR1 conducting without input. |
