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US 7,746,239 B2Granted
Light scattering type smoke detector
AssigneeHochiki Corporation
InventorTetsuya Nagashima
Life of this patent
Estimating the term…
Abstract
A light scattering type smoke sensor includes a sensor body, light-emitter for emitting light toward an open smoke-sensing space and outputting a light-received signal according to the amount of scattering light received, and a fire judging unit for judging whether fire occurs or not on the basis of the amount of received light determined on the basis of the outputted light-received signal.
Claims18
A light scattering type smoke sensor comprising:
- a sensor body;
- a light-emitting opening and a light-receiving opening that are disposed on an outer surface of the sensor body;
- a transparent cover that is attached to the outer surface of the sensor body for covering the light-emitting opening and the light-receiving opening;
- a light-emitter that is incorporated in the sensor body;
- a light-receiver that is incorporated in the sensor body;
- and
- a fire judging unit that is incorporated in the sensor body, wherein:
- the light-emitter is configured for emitting light toward a smoke-sensing point that is set in an open smoke-sensing space located outside the transparent cover via the light-emitting opening;
- the light-receiver is configured for receiving scattered light generated by the light emitted from the light-emitter to the smoke-sensing point via the light-receiving opening, and to output a light-received signal corresponding to an amount of received light scattered;
- and
- the fire judging unit is configured for judging presence/absence of fire occurrence based on the amount of received light identified by the light-received signal output from the light-receiver.
8 more elements
A light scattering type smoke sensor comprising:
- a sensor body;
- a light-emitter that is incorporated in the sensor body to emit light toward an open smoke-sensing space located outside the sensor body;
- a light-receiver that is incorporated in the sensor body to receive scattered light generated by the light emitted from the light-emitter to the smoke-sensing space, and to output a light-received signal corresponding to an amount of received light scattered;
- and
- a fire judging unit that judges presence/absence of fire occurrence based on the amount of received light identified by the light-received signal output from the light-receiver;
- wherein:
- the fire judging unit judges the present/absence of the fire occurrence based on the amount of received light and a differential value of the amount of received light;
- the fire judging unit judges that fire occurs when the amount of received light exceeds a predetermined fire threshold and the differential value of the amount of received light is equal to or lower than a predetermined false alarm threshold;
- and
- when the amount of received light exceeds the predetermined fire threshold, and the differential value of the amount of received light exceeds the predetermined false alarm threshold, the fire judging unit checks whether the amount of received light exceeds a predetermined obstacle threshold or not when a predetermined time elapses since the time the differential value exceeds the predetermined false alarm threshold, and judges that there is an obstacle for fire sensing when the amount of received light exceeds the obstacle threshold.
7 more elements
A light scattering type smoke sensor comprising:
- a sensor body;
- a light-emitter that is incorporated in the sensor body to emit light toward an open smoke-sensing space located outside the sensor body;
- a light-receiver that is incorporated in the sensor body to receive scattered light generated by the light emitted from the light-emitter to the smoke-sensing space, and to output a light-received signal corresponding to an amount of received light scattered;
- and
- a fire judging unit that judges presence/absence of fire occurrence based on the amount of received light identified by the light-received signal output from the light-receiver, wherein:
- the light-emitter comprises a first light-emitter that emits light of a first wavelength, and a second light-emitter that emits light of a second wavelength which is shorter than the first wavelength;
- and
- a first scattering angle formed by mutual crossing of a light axis of the first light-emitter and a light axis of the light-receiving element is smaller than a second scattering angle formed by mutual crossing of a light axis of the second light-emitter and the light axis of the light-receiving element.
5 more elements
A light scattering type smoke sensor comprising:
- a sensor body;
- a light-emitter that is incorporated in the sensor body to emit light toward an open smoke-sensing space located outside the sensor body;
- a light-receiver that is incorporated in the sensor body to receive scattered light generated by the light emitted from the light-emitter to the smoke-sensing space, and to output a light-received signal corresponding to an amount of received light scattered;
- and
- a fire judging unit that judges presence/absence of fire occurrence based on the amount of received light identified by the light-received signal output from the light-receiver, wherein:
- the light-emitter comprises a first light-emitter and a second light-emitter;
- the first light-emitter emits light having a polarization plane vertical to a first scattering plane that passes through a light axis of the first light-emitter and a light axis of the light-receiving element;
- the second light-emitter emits light having a polarization plane parallel to a second scattering plane that passes through a light axis of the second light-emitter and the light axis of the light-receiving element;
- and
- a first scattering angle formed by mutual crossing of the light axis of the first light-emitter and the light axis of the light-receiving element is smaller than a second scattering angle formed by mutual crossing of the light axis of the second light-emitter and the light axis of the light-receiving element.
7 more elements
Dependencies are inferred from the claim text.