Engine Governors.—Probably the oldest and best known governor for regulating the inlet of steam to an engine, is what is known as the Watt design. This is shown in [Fig. 68].
The pedestal A which supports the mechanism, has an upwardly-projecting stem B, to the upper end of which is a collar C, to which the oppositely-projecting pendent arms D are hinged. These arms carry balls E at their free ends.
The lower part of the stem has thereon a sliding collar F, and links G, with their lower ends hinged to the collar, have their upper ends attached to the swinging arms D. The collar has an annular groove at its lower end, to receive therein the forked end of one limb of a bell-crank lever H, the other limb of this lever being connected up with the engine throttle, by means of a link L.
Centrifugal motion serves to throw out the balls, as indicated by the dotted lines J, and this action raises the bell-crank lever, and opens the throttle valve.
Numerous types of governors have been constructed, some of which operate by gravity, in connection with centrifugal action. Some are made with the balls adapted to swing downwardly, and thrown back by the action of springs. Others have the balls sliding on horizontally-disposed arms, and thrown back by the action of springs; and gyroscopic governors are also made which are very effective.