Pressure operated modulating meter for regulating a flue damper

Claim 1

The combination of a modulating control meter and a draft control comprised of a pivotally operated pointer gauge that is responsive to fluctuating fluid draft conditions, said gauge including a fluid pressure responsive device to indicate an increase or decrease in pressure of fluid, said fluid pressure device including a diaphragm that is reSponsive to changes in fluid pressure, said diaphragm connected to a pointer in said gauge, said pointer pivotally mounted to be moved clockwise or counter-clockwise by said diaphragm as it responds to changes in fluid pressure, a shutter vane mounted integral with said pointer to move pivotally with said pointer, a freely movable arm pivotally mounted on the same pivot as said pointer and supporting a pair of spaced apart electro-optical photo-cells that are positioned to face toward said shutter, said photo-cell supporting arm connected to a manually adjustable knob to permit pivotally moving said arm clockwise or counter-clockwise to a desired setting, a pair of lamps to provide light rays to activate said photo-cells, said pair of lamps located below said shutter, said shutter vane movable about a central axis and having a configuration that provides an intercepting cover portion for both of said photo-cells in a predetermined position and is so shaped as to uncover one photo-cell only when turned counter-clockwise and so shaped as to uncover the other photocell only when turned clockwise thus activating either photo-cell according to the direction of movement of said pointer and shutter, each photo-cell connected to an electronic switch and each switch connected to a reversible motor for draft control, means to drive said reversible motor in either direction to control said draft and means to indicate the result of said control.