Flame detection system using oscillating element

Claim 1

IN APPARATUS OF THE CHARACTER DESCRIBED FOR DETERMINING THE PRESENCE OF A FLAME WHICH HAS AN EMISSION BAND IN ITS SPECTRUM WHEREIN THE INTENSITY OF RADIATION CHARGES RATHER ABRUPTLY WITH RELATIVELY LITTLE CHANGE IN FREQUENCY, MEANS FOR PRODUCING SAID FLAME HAVING SAID EMISSION BAND, LIGHT DISPERSING MEANS FOR DISPERSING RADIATION FROM THE FLAME INTO A SPECTRUM, PHOTOCELL MEANS, MEANS SELECTING FROM SAID SPECTRUM SUBSTANTIALLY ONLY THAT RADIATION WHICH IS CHARACTERISTIC OF SAID EMISSION BAND OF SAID FLAME AND FOR APPLYING SAID SELECTED PORTION TO SAID PHOTOCELL, MEANS VIBRATING SAID SELECTING MEANS AT A RECURRENT FREQUENCY TO DEVELOP AN OUTPUT SIGNAL IN SAID PHOTOCELL WHICH VARIES AT SAID RECURRENT FREQUENCY AND AT AN AMPLITUDE DETERMINED SUBSTANTIALLY ONLY IN ACCORDANCE WITH AND IN PROPORTION TO THE AMPLITUDE OF RADIATION IN SAID EMISSION BAND, TUNED AMPLIFYING MEANS COUPLED TO SAID PHOTOCELL AND TUNED TO SAID RECURRENT FREQUENCY FOR DEVELOPING AN AMPLIFIED SIGNAL, AND VOLTAGE RESPONSIVE MEANS COUPLED TO SAID AMPLIFYING MEANS AND CONTROLLING SAID FLAME.