| 摘要 |
A smoke detector has a plurality of labyrinth members (9) forming smoke inlet passages which block ingress of external light, a central smoke detecting chamber, a light emitter (12) and a light detector (13) disposed so that their optical axes intersect at the centre of the smoke detecting chamber, and a light shield (14) for preventing emitter light reaching the detector directly. The end (92) of a labyrinth member adjacent to the smoke detecting chamber is bent so that a side (93) lies parallel to a side (91) of an adjacent labyrinth member. Light from the emitter entering the passage (95) so formed between adjacent labyrinth members is repeatedly reflected away from the detecting chamber, therefore lowering the zero-point level output for light scattered by smoke and enhancing the reliability of the smoke detector. The outer end of the labyrinth member may be bent to increase light reflections and consequent attenuation. |
