draught regulator, draft regulator

A means for opening and closing furnace-doors, or dampers in the air, draught, or discharge flue, so as to urge the fire or moderate its intensity, respectively, as it may lag below or quicken above the desired standard. Automatic devices for this purpose are actuated by arrangements known as thermostats. These usually depend upon the expansion of metal by heat and its consequent contraction as it cools. The lengthening or shortening of a metallic rod is the actuating force which is communicated by levers or other mechanism to the door, register, or damper. As a certain relation exists-under ordinary conditions-between the heat of steam and its pre ure, the heat or pre ure of steam acting on a column of mercury may be made by electric connection to actuate a magnet, and so operate the device which governs acce of air to the furnace, or determines the area of the flue by which the volatile results of combustion are discharged. [DAM PER.] draught-rod, draft-rod, s. Plow.: A rod extending beneath the beam from the clevis to the sheath and taking the strain off the beam.