Chambers A and D of the regulator are separated by membrane 1, chambers B and F, by membrane 2 and chambers D and B, by bellows 3. The membranes and bellows are linked to rod 4. Chamber D is connected to the atmosphere, and chambers B and F are connected together through throttling aperture a. When the level of the liquid in vessel 13 drops, bell-crank lever 5 turns clockwise and shifts valve member 6 upward. Compressed air, delivered to the valve, is admitted into chamber A. This bends membrane 1 downward together with rod 4. The rod turns rocker arm 7 which opens valve 8 to admit compressed air. Valve 9 remains closed. The pressure in chamber F increases and is transmitted to servomotor 10 where it bends membrane 11 downward. This opens valve member 12, increasing the supply of liquid to vessel 13. As a result of the gradual flow of air from chamber F to chamber B, rod 4 is displaced a certain distance more, until the pressure in chamber A becomes equal to the initial pressure.
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