Infrared dynamic flame detector

Claim 2

An infra-red dynamic flame detector for use with fossil fuel fired burners in a furnace formed with walls having port openings for receiving said burners comprising: Infra-red sensor means responsive to energy of a selected bandwidth 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 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 infrared 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 regulated DC voltage supply means and amplifier means responsive to the output of the cell for converting the variable infrared 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 configuraation 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 infrared dynamic flame detector according to claim 6 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 infrared dynamic flame detector according to claim 5 in which said cell resistance changes in accordance with fluctuations in the infrared 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.

Claim 11

An infrared dynamic flame detector according to claim 1 adapted for use in a coal fired furnaCe in which formations of smoke and coal dust are formed in the combustion zone of said furnace, in which an optical nipple of the infrared sensor is sized for mounting outside of said combustion zone such that the unit is effectively protected from damage by the intense flame of the burner.

Claim 12

An infrared dynamic flame detector according to claim 1 in which the furnace is fired with gas having an oil fired ignitor associated with the gas burner; and said infrared sensor includes a photosensitive cell for converting infrared radiation from said oil fired ignition to fluctuations, whereby the means responsive to the AC signal distinguishes between the oil fired ignition and the gas fired combustion, indicating whether said oil fired ignition is in actual operation.

Claim 13

An infrared dynamic flame detector according to claim 1 in which the amplifier means amplifies the AC signal corresponding in frequency to the flame fluctuations, and wherein the means responsive to the AC signal comprises a filter circuit having the aforementioned frequency response of about 45 to 60 CPS that is rich in primary combustion zone frequencies, with the background frequencies falling outside of such response range, being attenuated by the filter circuit.