Smoke detector

US7940190B2 · kind B2 · utility

Assignee

• Thorn Security Limited · GB

Inventor

• Stephen John Penney · Chelmsford, GB

Key dates

• Filing date: Dec 12, 2005
• Grant date: May 10, 2011
• Expiry date: Apr 11, 2027

Classification

• Technology area (CPC G): Physics
• CPC primary: G08B29/043
• WIPO field: Control
• WIPO sector: Instruments

Abstract

A self-monitoring smoke detector comprising a housing (11) defining an internal chamber (12). An optical transmitter (13) is mounted within the housing (11) so as to direct light into the optical chamber (12). An optical receiver (14) is mounted in the housing (11) and in optical communication with the optical chamber (12). The optical transmitter (13) and the optical receiver (14) are so positioned that light from the transmitter cannot directly reach the receiver. Monitoring means is provided, comprising first and second light-scattering means (13a and 14a) positioned respectively in alignment with the transmitter (13) and the receiver (14). The arrangement is such that, in the absence of reflector particles in the optical chamber, light from the transmitter (13) can reach the receiver (14) only after scattering at the first light-scattering means (13a) and then after scattering at the second light-scattering means (14a).