| 摘要 |
PURPOSE:To check at all times a light beam type safety device by generated check pulses with a predetermined interval to prevent luminescence of a luminescent element and judging at that moment whether or not the light shielding signal is outputted. CONSTITUTION:Luminescent elements 16a-16c succesively emit lights through a light projection pulse generating circuit 10 by a distributing circuit 12 to form a light beam curtain in the danger area of a press machine and so on. When the light is shielded, the output from light receiving elements 18a-18c becomes zero, and the levels of the outputs of hold circuits 24a-24c fall to a low level and a relay R is deenergized to stop the press machine. A check pulse generating circuit 30 generates check pulse with a set interval to suppress luminescence of the luminescent elements 16a-16c and at the same time outputs judgemnt pulse to a judgemet circuit 32. When the judgement circuit 32 receives this pulse, it outputs abnormality signal to stop the press machine and energizes a luminescent diode 36 to display abnormality, if the output of the hold circuit 24 is at a low level, namely an OR circuit 34 does not output light shielding signal. |
