RICHARD G THOMAS, MD
Medical Practice in Cleveland, OH

5581241, Dec 3, 1996

Aug 12, 1994

8/289659

Michael Kaufman - Cleveland Heights OH
Richard W. Thomas - Bedford OH

Voice Products Inc. - Cleveland OH

G08B 1710

340630

A smoke detector that operates on the principle of scattered light is disclosed that has the capability of an operating sensitivity that is tens of times greater than that of smoke detectors presently available. Plural light sources are used, their light rays directed radially toward the center of a cylindrical detector chamber having a mirrored wall that reflects light back toward the chamber's center, thereby to brightly illuminate a central detection zone. Scattered light from smoke in this zone is detectable by a photocell at right angles to the converging multiple light rays. To obtain highly improved stability of the light output that enables ultra-high sensitivity, the light sources are light-emitting diodes in series connection and they are driven by a very stable constant voltage source that also powers the photocell detector. This system gains impressive sensitivity while reducing nuisance alarms that have been a common problem regarding efforts to increase smoke detector sensitivity. Whereas the goal of this invention is to improve the public safety, improvements are presented in smoke collection also, whereby ambient air is quickly and efficiently brought to the detector cell itself using convection currents that are enhanced by the aerodynamic design of the housing surrounding the cell.