Smoke detector

Details Smoke detector Smoke detector

2008-03-04

2010-11-16

Pham, Toan N (Department: 2612)

Communications: electrical

Condition responsive indicating system

Specific condition

C340S628000, C340S693600

Reexamination Certificate

active

07834773

ABSTRACT:
A smoke detector having a structure in which, at a time of performing smoke detection, an S/N ratio of a signal of a light receiving element is improved, to thereby accurately detect the occurrence of a fire. At opposite end portions of an inside of an optical case (21) having a substantially cylindrical shape, a light emitting element (11) and a stray light portion (22) are arranged. In the stray light portion (22), a light trap (23) is provided. Further, in the vicinity of the light emitting element (11), a condenser lens (24) is provided to allow light L to be incident on a curved surface of the light trap (23). At the time of smoke detection, light scattered by smoke particles in a smoke detection portion (25) is received by a light receiving element (12). However, the light that is incident on the light trap (23) is reflected on the curved surface a plurality of times to be attenuated in each reflection, so the light is not received by the light receiving element (12). Accordingly, the S/N ratio of an output signal S obtained from the light receiving element (12) is improved, thereby making it possible to accurately perform smoke detection at an early stage.

REFERENCES:
patent: 4857895 (1989-08-01), Kaprelian
patent: 5598147 (1997-01-01), Mochizuki et al.
patent: 5610592 (1997-03-01), Okazaki
patent: 6285291 (2001-09-01), Knox et al.
patent: 6288647 (2001-09-01), Yamano

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