Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1992-08-21
1993-09-14
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
2502221, 340556, 324177, G01V 904, G08B 1318
Patent
active
052451780
ABSTRACT:
An apparatus and method for automatically testing a safety light curtain used to protect to an unsafe moving part of an industrial machine. A combined beam splitter and photodetector is temporarily attached to the receiver of the light curtain with beam splitter in the path of one of the light beams. A portion of the light beam continues to a receiver of the light curtain and a diverted portion of the light beam illuminates a photodetector. Interruption of this particular light beam simultaneously triggers a safety system to initiate the stopping of the machine and triggers the photodetector. A motion detector temporarily coupled to a rotating part of the machine determines when the machine has stopped. This motion detector may include a d.c. tachometer coupled via a resilient friction wheel. A timer connected to the photodetector and the motion detector determines the duration of the interval between interruption of the one light beam and the stopping of the machine. Either this time or a computed safety distance based upon a predetermined hand speed is displayed. This measured time or the computed distance can be used to determine if the light curtain is positioned far enough from any dangerous moving parts of the machine so that an emergency stoppage of the machine protects the operator from harm.
REFERENCES:
patent: 3746863 (1973-07-01), Pronovost
patent: 4249074 (1981-02-01), Bettler et al.
patent: 4446602 (1984-05-01), Marx et al.
patent: 4520262 (1985-05-01), Denton
patent: 4818866 (1989-04-01), Weber
patent: 5015840 (1991-05-01), Blau
MagneTek Controls
Messinger Michael
Nelms David C.
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