A labyrinthine light scattering-type smoke detector

Claim 1

A labyrinthine light-scattering-type smoke detector comprising a generally cylindrical housing including end walls and a labyrinthine side wall, a light projecting element and a light receiving element within said housing labyrinthine side wall, a light shield member interposed between said light projecting and receiving elements, said side wall being formed of a plurality of identical light shielding columns each having a generally J-shaped cross section arranged in a circle, said J-shaped cross section including a head portion, a leg portion and a rear portion in proceeding radially outwardly of said housing with each portion being defined by parallel planar surfaces, the head portion of each of said light shielding columns having a first reflecting point thereon, each head portion being inclined relative to the bisector of an angle between a pair of lines intersecting at said first reflecting point and connecting said first reflecting point with said projecting element and said light receiving element to provide a radially inward end part and a radially outward end part of said head portion, said radially outward end part of said head portion being disposed within a space defined by the head and leg portions of an adjacent light shielding column, said light shielding columns having darkly colored light reflecting surfaces.