Fire monitoring system

• US 4,972,178 A
• Filed: 04/04/1989
• Issued: 11/20/1990
• Est. Priority Date: 04/05/1988
• Status: Expired due to Fees

• Current Assignee: Nittan Co. Ltd. (Old) (Secom Company Limited)
• Original Assignee: Nittan Co. Ltd. (Old) (Secom Company Limited)
• Inventors: Suzuki, Takashi
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Sutcliffe, Geoff
• Application Number:
  US07/332,744
• Time in Patent Office: 595 Days
• Field of Search: 340/577, 340/584, 340/587, 374/117, 374/118, 374/119
• US Class Current: 340/577
• CPC Class Codes: G01K 11/24 of the velocity of propagation of sound
• CPC Class Codes: G08B 17/00 Fire alarms; Alarms responsive to explosion
• CPC Class Codes: G08B 17/06 Electric actuation of the alarm, e.g. using a thermally-operated switch

Abstract

In a fire monitoring system for monitoring the occurrence of a fire in which a space to be monitored is imaginarily subdivided into plural subspaces so that plural channels passing through the subspaces are set so as to intersect to each other in a lattice form. The propagation speed of ultrasonic waves propagating through each of the channels is measured, on the basis of which the propagation speed of the ultrasonic waves in each of the subspaces is calculated in the same manner as the solution for each element of a matrix is obtained, and then the temperature in each of the subspaces is obtained. By providing the system with a humidity sensor, the temperature for a dry condition is obtained.

Claims

1. A fire monitoring system for monitoring the occurrence of a fire, comprising the steps of:

imaginarily subdividing a space to be monitored into plural subspaces so that plural channels passing through a plurality of arbitrary subspaces are set so as to intersect each other in a lattice form;

measuring a first propagation speed of ultrasonic waves propagating through each of said channels;

calculating a second propagation speed of the ultrasonic waves in each of said subspaces using a mathematical method in which the first propagation speeds and variables for the second propagation speeds are placed into matrices and the solution to an equation involving the matrices, which yields the second propagation speeds, is carried out with matrices; and

determining a temperature in each of said subspaces on the basis of said second propagation speed.

2. A fire monitoring system as claimed in claim 1, wherein at least two pairs of ultrasonic wave generators and ultrasonic wave receivers are arranged so that one of said two pairs is located in one of said channels and the other is located in another channel vertically intersecting the channel.

3. A fire monitoring system as claimed in claim 2, wherein said at least two pairs are moved in directions perpendicular to each other, to thereby measure all of said first propagation speeds.

4. A fire monitoring system as claimed in claim 2, wherein plural pairs of ultrasonic wave generators and ultrasonic wave receivers are arranged so that all of said pairs are assigned to all of said channels

5. A fire monitoring system as claimed in claim 1, said system further comprising the step of:

measuring humidity within the space to be monitored and correcting said first propagation speed into a propagation speed for a dry condition.

6. A fire monitoring system for monitoring the occurrence of a fire, comprising:

ultrasonic wave generating means for emitting ultrasonic waves into a space to be monitored;

speed measuring means for measuring a first propagation speed of the ultrasonic waves in the space;

humidity measuring means for measuring humidity within the space;

correcting means for correcting said first propagation speed on the basis of the measured humidity data and obtaining a second propagation speed for a dry condition; and

temperature computing means for computing the temperature in the space on the basis of said second propagation speed.

7. A fire monitoring system as claimed in claim 6, said system further comprising alarming means for comparing a signal from said temperature computing means with a predetermined signal and generating a fire monitoring signal when said signal is equal to or higher in level than said predetermined signal.

8. A fire monitoring system as claimed in claim 6, wherein said humidity measuring means comprises a humidity sensor.

9. The fire monitoring system of claim including ultrasonic wave receiving means positioned in relationship to said ultrasonic wave generating means so as imaginarily to divide said space into a plurality of subspaces.