Flame detector

• US 4,463,260 A
• Filed: 10/05/1981
• Issued: 07/31/1984
• Est. Priority Date: 10/18/1980
• Status: Expired due to Fees

• Current Assignee: Horiba Limited
• Original Assignee: Horiba Limited
• Inventors: Ikeda, Tosiaki
• Primary Examiner(s): Smith, Alfred E.
• Assistant Examiner(s): FIELDS, CAROLYN
• Application Number:
  US06/308,853
• Time in Patent Office: 1,030 Days
• Field of Search: 250/349, 250/339, 250/340, 250/341, 340/578
• US Class Current: 250/339.15
• CPC Class Codes: G08B 17/12 Actuation by presence of radiation or particles, e.g. of infrared radiation or of ions

Abstract

A flame detector, in which the generation of a flame is detected by detecting the level of radiant rays at the wavelength characteristic of flame, of infrared rays radiated from the objects generating the flame and in a valley between both of the wavelengths by means of infrared detectors and judging from the comparison of the outputs of the detectors, whether or not there is a valley in the spectrum.

The construction of a flame detector according to the present invention can surely detect flame merely by comparing three quantities of radiant rays at three wavelengths without false alarms and accordingly, an element for setting a standard value is not required. This results in a flame detector having a remarkably simple construction.

Claims

1. A flame detector comprising:

first and second and third infrared detectors, said detectors arranged to respectively detect radiation at first, second, and third wavelengths;

first and second comparators operatively connected to said first and second and third detectors, said first comparator providing an output when an output of said first detector is greater than an output from said second detector and said second comparator arranged to provide an output when an output of said third detector is greater than said output from said second detector;

an AND gate operatively connected to said outputs of said first and second comparators for providing an output when said first and second comparators provide an output;

wherein said first wavelength is arranged to be equal to a wavelength of radiation emitted by an object generating a flame to be detected and wherein said third wavelength is arranged to be equal to a wavelength of radiation emitted by said flame to be detected and said second wavelength is arranged to be between said first and third wavelengths, whereby said flame detector detects a valley in the spectrum of infrared radiation emitted from an object generating a flame, said valley in said spectrum being characteristic of an object which is generating a flame and said valley not being present in a heated object which is not generating a flame.

2. A flame detector as recited in claim 1, wherein said infrared detectors comprise pyroelectric infrared detectors.

3. A flame detector as recited in claim 1, wherein said infrared detectors comprise semiconductor infrared detectors.

4. A flame detector as recited in claim 1, wherein said first wavelength is in the range of from 2 to 3 microns and wherein said third wavelength is about 4.3 microns.