Fire detector

• US 5,986,556 A
• Filed: 05/23/1997
• Issued: 11/16/1999
• Est. Priority Date: 05/25/1992
• Status: Expired due to Term

• Current Assignee: Nohmi Bosai Limited (Secom Company Limited)
• Original Assignee: Nohmi Bosai Limited (Secom Company Limited)
• Inventors: Yasukawa, Makoto, Hirooka, Eiji, Mochizuki, Mikio
• Primary Examiner(s): Lefkowitz, Edward
• Application Number:
  US08/862,406
• Time in Patent Office: 907 Days
• Field of Search: 340/630, 340/628, 250/573, 250/574
• US Class Current: 340/630
• CPC Class Codes: G08B 17/107 for detecting light-scattering due to smoke

Abstract

A fire detector capable of readily and accurately adjusting the sensitivity there of and of not erroneously outputting any fire signal is provided with a first-stage amplifying circuit having an output adjusting variable resistor and a fire discriminating section having a reference voltage adjusting variable resistor. As a result, it is possible to adjust the amplified output to a predetermined value by the switching level of the fire discriminating section to a predetermined value by the reference voltage adjusting variable resistor.

Claims

1. A photoelectric type fire detector comprising:

a light-emitting section for generating pulsed light for detecting smoke;

a light-receiving section, having a first variable resistor, for receiving scattered light from the light from said light-emitting section caused by the smoke, amplifying a light-receiving output, and adjusting a gain;

an A/D converting circuit for converting the light-receiving output from said light-receiving section into digital signals; and

a signal transmitting section, having an operation indicating lamp, for transmitting the digital signals having been converted in said A/D converting circuit;

wherein said light-emitting section comprises a light-emitting element for detecting smoke, an oscillating circuit for making said light-emitting element emit light by supplying a pulse output thereto, and a pulse width expanding circuit for expanding a pulse width of the pulse output from said oscillating circuit and outputting it to said operation indicating lamp.

2. A heat-photoelectric type fire detector comprising:

a light-emitting section for generating pulsed light for detecting smoke;

a light-receiving section, having a first variable resistor for adjusting an output, for receiving scattered light of the light emitted from said light-emitting section;

a heat detecting section for detecting heat by a heat-sensitive element;

an A/D converting circuit for converting the output from said light-receiving section and a detected output from said heat detecting section into digital signals; and

a signal transmitting section, having an operation indicating lamp, for transmitting the converted digital signals from said A/D converting circuit;

wherein said light-emitting section comprises a light-emitting element for detecting smoke, an oscillating circuit for making said light-emitting element emit light by supplying a pulse output thereto, and a pulse width expanding circuit for expanding a pulse width of the pulse output from said oscillating circuit and supplying it to said operation indicating lamp.