Light scattering type smoke detector

Abstract

A light scattering type smoke detector having an improved labyrinth high in shielding effects for interior detecting means from the exterior light and other obstacles such as dusts, insects or the like than smoke particles is provided. The labyrinth comprises a plurality of outer peripheral shielding elements spaced from one another defining peripheral apertures therebetween, a plurality of inner shielding elements spaced from the outer elements and from one another defining therebetween inner apertures, said inner shielding elements opposing respectively to each peripheral aperture and said inner apertures to each outer shielding element, and a filtering means made of thin plate material perforated to have many small holes and disposed behind the respective outer elements to close the inner apertures while allowing substantially the smoke particles only to pass therethrough. In an aspect, the inner shielding elements and filtering means comprise an integral strip-shaped plate substantially of ring shape perforated at spaced sections providing therebetween non-perforated shielding sections, and the respective outer shielding elements have an inward extended wall to guide incoming smoke toward the filtering perforated sections.