Electricity: electrical systems and devices – Safety and protection of systems and devices
Patent
1982-07-19
1984-07-31
Shoop, William M.
Electricity: electrical systems and devices
Safety and protection of systems and devices
34081514, H02H 700
Patent
active
044633980
ABSTRACT:
An intrinsically safe or an explosion proof pilot light having a cluster of light emitting diodes arranged in a pattern and visible through a lense cap located in a hazardous area. The pilot light has terminals connected through a rectifying bridge and a current regulator to the diodes to optimize the light output of the diodes and make the pilot light insensitive to the polarity or variations in the voltage of the A.C. or D.C. electrical supply to the pilot light and limiting the current to the diodes to a constant value in event one or more of the diodes is destroyed or shorted. A pair of printed circuit boards are spaced by a plurality of conductive supports with one of the boards mounted on a base of the pilot light and carrying the rectifier and current limiting components which are connected to the terminals. The other printed circuit board provides a support for the diodes and has a printed circuit thereon, portions of which provide a reflective surface for light emitted by the diodes. The pilot light includes a translucent lense cap formed of material that transmits light frequencies matching the light frequencies emitted by the light emitting diodes and optionally may include a fuse that replaces one of the conductive supports and limits current to the hazardous area.
REFERENCES:
patent: 2529706 (1950-11-01), Pearson
patent: 3059231 (1962-10-01), Arneberg et al.
patent: 3435449 (1969-03-01), Sloan
Boozer James M.
Franks Terry E.
Rothweiler Richard C.
Guttman Richard T.
Schmeling William H.
Shoop William M.
Square D Company
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