Apparatus for detecting the passage of glowing embers

• US 4,233,504 A
• Filed: 08/03/1978
• Issued: 11/11/1980
• Est. Priority Date: 08/03/1978
• Status: Expired due to Term

• Current Assignee: Detector Electronics Corporation
• Original Assignee: Chloride Incorporated
• Inventors: Kalns, Rudolph W.
• Primary Examiner(s): Nelms, David C.
• Application Number:
  US05/930,606
• Time in Patent Office: 831 Days
• Field of Search: 250/214 B, 250/214 RC, 250/, 250/573, 250/574, 250/575, 250/554, 340/630
• US Class Current: 250/214.0RC
• CPC Class Codes: G08B 17/12 Actuation by presence of radiation or particles, e.g. of infrared radiation or of ions

Abstract

An infrared detector of sufficient sensitivity and stability to provide for the reliable detection of a glowing ember moving through an enclosed carrier system (duct or conveyor) in which a photo-resistive device for viewing the interior of the carrier is connected into suitable circuitry that does not respond to slowly changing ambient light, but which produces a voltage pulse in response to a moving glowing ember passing through the field of view of the detector; said voltage pulse being utilized to provide an output signal which may actuate an alarm or release extinguishant.

Claims

1. A duct system comprising an opaque wall portion and a detector for detecting a single glowing ember travelling through said opaque wall portion, said detector comprising a photo-resistive cell connected in series with a resistor across a voltage supply, the voltage at the junction between the cell and resistor varying as a function of the resistance of the cell, said junction being coupled to the input of an AC responsive device through a differentiator, whereby an ember moving through the field of view of the photo-resistive device causes a drop in resistance of the cell to cause a voltage change at the junction, the input and output of said AC responsive device being proportional to the rate of change of said voltage change at the junction, and means responsive to an output of said AC responsive device above a predetermined magnitude to actuate an alarm.

2. A duct system for conveying flammable particulate material of the type which is susceptible to containing glowing embers of said particulate material, said system including a portion with an opaque wall, a plurality of optical detectors disposed at circumferentially spaced positions around said opaque wall and viewing the interior thereof, each of said detectors comprising a photo-resistive cell connected in series with a resistor through a junction across a voltage supply, whereby a change of resistance of said photo-cell occurs when the photo-cell views a glowing ember travelling in the duct causing a corresponding change in voltage at said junction, differentiator means connected to said junction which produces an output voltage which is a function of the rate of change of said junction voltage and means responsive to a rate of change of predetermined amplitude to actuate an alarm.

3. A detector system for detecting and providing an output response in response to a single suddenly-occurring optical phenomenon of short duration, comprising a photo-responsive cell connected with suitable circuitry to provide a first voltage pulse in response to the viewing of said phenomenon by said cell said first pulse having a rise time which is a function of the speed of occurrence of said phenomena, means responsive to said first pulse to provide a second pulse having a maximum value which is a function of the rate of change of the voltage of said first pulse, amplifier means receiving said second pulse and an electronic switching means receiving the amplifier output, said electronic switching means being responsive only to an amplifier output above a predetermined value to shift from a first condition to a second condition, said predetermined value of the amplifier output being produced only by a first pulse having a rate of voltage increase above a predetermined rate.