Improvements in flame responsive means

861,564. Controlling burners. BABCOCK & WILCOX Ltd. May 28, 1957 [May 28, 1956; Ang. 13, 1956]. Nos. 16416/56 and 24723/56. Class 75 (1). A microphone 23 responsive to the noise of the flame of a burner 6 is adapted to actuate an alarm 30 or to control a fuel valve when the noise exceeds a predetermined level which is varied in accordance with the rate of fuel supply to the burner. The rate of fuel supply is arranged to provide a D.C. voltage which is compared with a D.C. voltage derived from the microphone in a comparator 28 and the resultant voltage is fed to a relay 29 controlling the alarm 30. The D.C. voltage from the fuel supply is provided by a potentiometer 44 which is actuated by a piston 34 moved against spring action by the pressure difference across a restriction 42 in the fuel supply line 31. The signal from the microphone is fed to an amplifier 25 connected to a frequency filter 26 connected to a rectifier 27. The microphone 23 is mounted on the outer end of a listening tube 21 extending through the outer wall 9 of an adjustable air register surrounding the burner 6.