Patent ID: 7442119
Filing Date: 2008-10-28
Classification: F24C

Abstract:
1. A ventilation device comprising: an exhaust hood comprising a drive unit for producing an air flow; a transmitter device affixed to a first side of the exhaust hood generating a laser light beam directed to a second side of the exhaust hood, wherein said transmitter device comprises a first lens through which said laser light beam passes through resulting in an expanded laser beam; a receiver device affixed to said second side, receiving said expanded laser light beam and generating an electrical signal in response, said receiver device comprising an optical sensor, wherein: a control device for receiving said electrical signal and controlling said drive unit, said control device comprising a processor for analyzing said electrical signal to determine a value determined by said number of maxima or minima light spots detected by said optical sensor over a time period, and controlling said drive unit in response to said value.