Optical smoke detector

An optical smoke detector comprising:

• a hollow cylindrical body having generally flat and parallel top and bottom spaced-apart portions and an intermediate generally circular side wall portion, and defining a closed smoke chamber having a plurality of inlets to allow the ingress and egress of smoke particles;
• radiation emitting means, mounted in the side wall portion of the cylindrical body, for projecting a direct beam of light into a test zone within the chamber, the light beam being substantially confined to said test zone away from said top, bottom and side wall portions of said body in the absence of smoke particles and, striking and bouncing off smoke particles in the test zone to produce scattered radiation;
• and radiation sensing means, mounted in the side wall portion of the cylindrical body, for detecting the scattered radiation from the smoke particles to facilitate the signalling of an alarm condition, said radiation sensing means being disposed so as not to directly receive said light beam projected by said radiation emitting means,
• the bottom portion of the body providing a flat lower surface, in the chamber, having a series of parallel grooves for accumulating undesired dirt and dust and for minimizing the reflection of the light beam off of that dirt and dust and toward the radiation sensing means, thereby to preclude false alarms.

An optical smoke detector comprising:

• a hollow cylindrical body having generally flat and parallel top and bottom spaced-apart portions and an intermediate generally circular side wall portion, and defining a closed smoke chamber having a plurality of inlets to allow the ingress and egress of smoke particles;
• radiation emitting means, mounted in the side wall portion of the cylindrical body, for projecting a direct and tightly focused beam of light into a test zone within the chamber;
• a reflector, mounted in the side wall portion directly opposite to and facing the radiation emitting means, for reflecting and refocusing the light beam back through the test zone and to the emitting means in the absence of smoke particles in the test zone, the direct and reflected beams being substantially confined to said test zone away from said top, bottom and side wall portions of said body in the absence of smoke particles, and striking and bouncing off any smoke particles in that test zone to produce scattered radiation;
• and radiation sensing means, mounted in the side wall portion of the cylindrical body, for detecting the scattered radiation from the smoke particles to facilitate the signalling of an alarm, said radiation sensing means being disposed so as not to directly receive the light beam projected by said radiation emitting means and reflected by said reflector,
• the bottom portion of the body providing a flat lower surface in the chamber having a series of parallel grooves for accumulating undesired dirt and dust and for minimizing the reflection of the light beam off of that dirt and dust and toward the radiation sensing means, thereby to preclude false alarms.