Infrared dynamic flame detector

Claim 2

An infra-red dynamic flame detector comprising: infra-red sensor means responsive to energy of a selected bandwith and providing an AC output signal in response thereto, means responsive to said AC signal for amplifying same when the frequency thereof falls between about 45 and 60 CPS and substantially rejecting all other signals, rectifier means for converting said amplified AC signal to a proportional DC level of the amplifier means output circuit means for comparing the DC output of the rectifier means with a selected limit value and delivering an appropriate output indicative thereof, time delay means responsive to said comparitor output for providing an output indicative of a flameout condition for a period longer than a selected delay of said time delay means, when the proportional DC signal falls below the selected limit whereby a flame momentarily affected by fluctuations in intensity may be detected.

Claim 3

The infra-red dynamic flame detector of claim 1 wherein said infra-red sensor includes an infra-red responsive cell and an optical nipple for coupling the infra-red energy of the flame thereto.

Claim 4

The infra-red dynamic flame detector of claim 2 further including a preamplifier for preamplifying the infra-red signals detected by the cell through said nipple and delivering an output signal therefrom.

Claim 5

The infra-red dynamic flame detector of claim 3 further including a remote receiver terminal unit for housing said amplifier means, rectifier means, signal detector means and time delay means and a conducting cable for coupling the output signals of said preamplifier to the amplifier of said remote receiver terminal unit.

Claim 6

The infra-red dynamic flame detector according to claim 3 wherein said preamplifier includes requlated DC voltage supply means and amplifier means responsive to the output of the cell for converting the variable infra-red radiation energy into a signal corresponding to a variable resistance, and output circuit means for delivering only the AC component of the signal corresponding to the variable resistance.

Claim 7

The infra-red dynamic detector according to claim 5 wherein said regulated DC voltage supply includes leads of opposite polarity, a resistor and a diode connected in series across said leads, a capacitor connected in a parallel circuit with said resistor for filtering said constant voltage, a resistor and transistor connected in series across said positive and negative leads, means connecting the base of said transistor to the negative side of said capacitor, so that a constant current source is provided for the cell which converts variable infra-red radiation to the corresponding variable resistance, a resistor and a transistor connected in series across said leads for generating a constant current source, two output transistors connected in a Darlington configuration across said leads, and to said last-named transistor for biasing the latter configuration with such constant current output, a transistor and a resistor connected in series across the cell circuit and output transistors to provide an impedance match, and a capacitor coupling only the AC component of the flame signal to the output transistors.

Claim 8

An infra-red dynamic flame detector according to claim 4 in which said cell is provided with a ground, positive and negative, leads each provided with quick disconnect terminal pin elements for mating with corresponding external socket elements, so that said cell can be easily removed and replaced.

Claim 9

An infra-red dynamic flame detector according to claim 4 including a housing for said optical nipple, preamplifier and cell and wherein said conducting cable is equipped with quick disconnect pin elements mating with corresponding circuit socket elements in said housing and remote terminal unit.

Claim 10

An infra-red dynamic flame detector according to claim 6 in which said cell resistance changes in accordance with fluctuations in the infra-red source intensity, which variable cell resistance together with the constant current generates a variable voltage at the positive terminal of said cell, such variable voltage then being coupled to the output transistors, thereby causing the latter to convert such voltage to variable current which constitutes the preamplified signal output, which is thereafter transmitted.