Automatic combustion control with improved electrical circuit

Claim 1

Smoke control apparatus comprising a combustion chamber, means for supplying fuel and oxygen containing gas into said chamber, means for venting the products of combustion from said chamber, smoke accumulating means for amplifying the density of said products of combustion to facilitate the detecting and measuring of the same, photoelectric means providing an electrical signal in accordance with the thusly amplified density of the products of combustion, electrical circuit means for processing said electrical signal, and servo-mechanism means operated by said circuit means to control the means for supplying fuel and oxygen containing gas to optimize the supply thereof and therefore said density; said circuit means comprising bridge means to control said servo-mechanism means, at least one first electronic switch operable when said density is equal to or less than a predetermined standard, at least one second electronic switch operable when said density is greater than said standard, said switches being coupled to and operating said bridge means, and further means coupled to and operating said bridge means, and further means coupled to said photoelectric means and to said switches to operate the latter in response to levels of said signal whereby to control said servo-mechanism means through said bridge means.