Light scattering smoke detector with smoke-entrance ladyrinth de

Details Light scattering smoke detector with smoke-entrance ladyrinth de Light scattering smoke detector with smoke-entrance ladyrinth de

1994-04-08

1995-07-04

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

340630, G01N 1506

Patent

active

054303079

ABSTRACT:
A smoke detector in which a plurality of labyrinth members are disposed on an upper wall in a standing position. In an area surrounded by the labyrinth members, a smoke detecting chamber is formed. A light emitting device and a light detecting device are disposed in such a manner that their optical axes intersect each other at the center of the smoke detecting chamber. In order for the visual field of the light detecting device with respect to the smoke detecting chamber to be restricted to the front area thereof, the labyrinth member which cross the optical axis of the light emitting device is formed so as to be longer than the other labyrinth members, and a gap is formed between the front end of the long labyrinth member and a light shielding plate for preventing the light emitted by the light emitting device from directly reaching the light detecting device. Therefore, the zero-point level of the detection output for light scattered by smoke is lowered to enhance the reliability and effectiveness of the smoke detector.

REFERENCES:
patent: 4216377 (1980-08-01), Hasegawa et al.
patent: 4397557 (1983-08-01), Herwig et al.
patent: 4469953 (1984-09-01), Fujisawa et al.
patent: 4758733 (1988-07-01), Mochizuki
patent: 4851819 (1989-07-01), Kawai et al.
patent: 4897634 (1990-01-01), Sawa et al.
patent: 5021677 (1991-06-01), Igarashi et al.

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