Patent ID: 7062953

Claim:
A sampling tube-type smoke detector comprising: an optical smoke detection device arranged to detect smoke particles contained in air suctioned through a sampling tube from a monitored area; an aspirator positioned downstream of said smoke detection device arranged to suction air through said sampling tube; a lead-in tube arranged to convey air from said sampling tube to said aspirator; said aspirator having an inlet and comprising a rotating part that sucks air through and discharges air from the lead-in tube and an actuator mechanism driving said rotating part in rotation about a rotational axis; said lead-in tube being connected directly to the air inlet of said aspirator through an expanded part of the lead-in tube and in which expanded part the flow path expands along the traveling direction of the air; said lead-in tube and said aspirator being oriented with the central axis of said lead-in tube and the rotational axis of said rotating part being substantially coaxial; said lead-in tube, optical smoke sensor unit and aspirator disposed in substantially a linear alignment; said lead-in tube has a substantially round-shaped cross-sectional form defining a lead-in tube inner wall surface; said lead-in tube and said expanded part are connected via a connection part of the lead-in tube defining a connection part inner wall surface; said connection part inner wall surface intersecting said lead-in tube inner wall surface and said expanded part inner wall surface along a smoothly contoured curve; said connection part is equipped with a restricted aperture defined by an aperture diaphragm opening smaller than the inside diameter of said lead-in tube central part; wherein the center of said aperture diaphragm opening is arranged substantially on the centerline of said lead-in tube; and said aperture diaphragm opening is disposed between said smoke sensor unit and said aspirator.