Bui. 1136, U. S. Dept. of Agriculture. 
Plate VI 
« 
Air-Operated Thermostat and Diaphragm Valve. 
The bulb A is connected to the flexible capsule B through the armored capillary tube C. 
Changes in the temperature of the bulb cause changes in the pressure of the liquid or gas in 
the bulb. The capsule expands and contracts accordingly, and moves a pivoted lever D, 
which opens and closes a small air valve E. Air at about 15 pounds pressure enters the sys- 
tem from the left, passes to the head F, and closes the steam valve G, the stem of which is 
connected to the diaphragm in the head. When the air valve E closes, the air supply to the 
diaphragm is shut off, the pressure is relieved by leakage through the valve E, and the spring 
II opens the steam valve. 
