FIRE ALARM SYSTEM
First Claim
1. A fire alarm system comprising:
- a sound wave generator sending a sound wave;
a sound wave detector being located so as to sandwich in a monitoring space between itself and the generator, the sound wave detector detecting the sound wave sent from the generator through the monitoring space;
a controller being configured to control the generator and the sound wave detector;
a processing circuit being configured to process an output detected by the sound wave detector, the processing circuit comprising a sound pressure detector for detecting a sound pressure based on the output, a smoke density estimator for estimating a density of smoke existing in the monitoring space and a fire alarm device being configured to transmit fire alarm when the smoke density estimated by the smoke density estimator exceeds a predetermined threshold;
wherein the generator and the sound wave detector are located in the monitoring space so as to form a first and second propagation paths for propagating the sound wave from the generator to the sound wave detector, the first and second propagation paths having different lengths each other,wherein the processing circuit comprises a calculation means for calculating a pressure ratio between a first sound pressure being a sound pressure of a sound wave propagated through the first propagation path and a second sound pressure being a sound pressure of a sound wave propagated through the second propagation path,wherein the smoke density estimator is configured to calculate a change ratio between the pressure ratio calculated by the calculation means and a predetermined average pressure ratio, and to determine the smoke density from the change ratio based on a predetermined relational expression, the relational expression describing the change ratio in relation to the smoke density.
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Accused Products
Abstract
A fire alarm system, determining existence or nonexistence of a fire by using an ultrasound wave, comprises a sound wave generator and a sound wave detector to detect sound waves propagated through two propagation paths having different lengths each other. The system comprises a calculation means for calculating a pressure ratio between a first sound pressure, which is a sound pressure of a sound wave propagated through a first propagation path, and a second sound pressure, which is a sound pressure of a sound wave propagated through a second propagation path, and a smoke density estimator. The smoke density estimator calculates a change ratio between the pressure ratio calculated by the calculation means and a predetermined standard pressure ratio, and determines a smoke density from the change ratio based on a predetermined relational expression describing the relation between the change ratio and the smoke density, and determines existence of a fire when the smoke density exceeds a predetermined threshold.
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Citations
12 Claims
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1. A fire alarm system comprising:
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a sound wave generator sending a sound wave; a sound wave detector being located so as to sandwich in a monitoring space between itself and the generator, the sound wave detector detecting the sound wave sent from the generator through the monitoring space; a controller being configured to control the generator and the sound wave detector; a processing circuit being configured to process an output detected by the sound wave detector, the processing circuit comprising a sound pressure detector for detecting a sound pressure based on the output, a smoke density estimator for estimating a density of smoke existing in the monitoring space and a fire alarm device being configured to transmit fire alarm when the smoke density estimated by the smoke density estimator exceeds a predetermined threshold; wherein the generator and the sound wave detector are located in the monitoring space so as to form a first and second propagation paths for propagating the sound wave from the generator to the sound wave detector, the first and second propagation paths having different lengths each other, wherein the processing circuit comprises a calculation means for calculating a pressure ratio between a first sound pressure being a sound pressure of a sound wave propagated through the first propagation path and a second sound pressure being a sound pressure of a sound wave propagated through the second propagation path, wherein the smoke density estimator is configured to calculate a change ratio between the pressure ratio calculated by the calculation means and a predetermined average pressure ratio, and to determine the smoke density from the change ratio based on a predetermined relational expression, the relational expression describing the change ratio in relation to the smoke density. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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Specification