Patent ID: 6756905
Filing Date: 2004-06-29
Classification: G08B

Abstract:
A photoelectric smoke detector comprising a case having mounted therein a circuit board and a smoke detection chamber having a side wall with a double row of generally rectangular vanes arranged to provide a labyrinth extending generally around the entire side wall for ingress and egress of smoke particles, a top and a bottom, a photoemitting diode mounted in a mounting arrangement in the side wall of the smoke detection chamber so that a light beam from the photoemitting diode is transmitted across the smoke detection chamber, the mounting arrangement extending and spaced away from the bottom to provide minimal interference for entry of smoke particles, the bottom of the smoke detection chamber having an opening therein with a shielding arrangement thereabout open to the chamber, the circuit board being mounted to overlie the bottom surface and including a photodiode detector mounted directly thereon and positioned generally in the opening so that it views into the smoke detection chamber through the opening and through the shielding arrangement, the shielding arrangement shielding the photodiode detector from incident light which may be present in the smoke detector chamber while providing for a diverging field of view of the photodiode detector which intersects the light beam of the photoemitting diode to define a detection volume contained within the smoke detection chamber, whereby the double vane side wall and spacing of the mounting arrangement from the bottom provides the smoke detection chamber with generally uniform smoke penetration properties around its entire periphery such that there is about a 5% or less variation in ability of smoke particles to penetrate the smoke detection chamber at any point around the periphery of the smoke detection chamber.