The Governor
On the right-hand end of the main shaft in Fig. [34] there will be seen a worm gear driving the governor. This is shown on a larger scale at A (Fig. [50]). At the left of the worm gear is a bevel gear driving the spindle D of the governor, and at the right an eccentric which gives a vibratory motion to the lever F. The crank C upon the end of the shaft operates the oil pump. The speed of the turbine is controlled by admitting the steam in puffs of greater or less duration according to the load. The lever F, having its fulcrum in the collar surrounding the shaft, operates with each vibration of the eccentric the pilot valve. The valve is explained in detail later.
FIG. 50
This form of governor has been superseded by an improved type, but so many have been made that it will be well to describe its construction and adjustment. The two balls W W (Fig. [50]) are mounted on the ends of bell cranks N, which rest on knife edges. The other end of the bell cranks carry rollers upon which rest a plate P, which serves as a support for the governor spring S. They are also attached by links to a yoke and sleeve E which acts as a fulcrum for the lever F. The governor is regulated by means of the spring S resting on the plate P and compressed by a large nut G on the upper end of the governor spindle, which nut turns on a threaded quill J, held in place by the nut H on the end of the governor spindle and is held tight by the lock-nut K. To change the compression of the spring and thereby the speed of the turbine the lock-nut must first be loosened and the hand-nut raised to lower the speed or lowered to raise the speed as the case may be. This operation may be accomplished while the machine is either running or at rest.
The plate P rests upon ball bearings so that by simply bringing pressure to bear upon the hand-wheel, which is a part of the quill J, the spring and lock-nut may be held at rest and adjusted while the rest of the turbine remains unaffected. Another lever is mounted upon the yoke E on the pin shown at I, the other end of which is fastened to the piston of a dash-pot so as to dampen the governor against vibration. Under the yoke E will be noticed a small trigger M which is used to hold the governor in the full-load position when the turbine is at rest.
The throwing out of the weights elevates the sleeve E, carrying with it the collar C, which is spanned by the lever F upon the shaft H. The later turbines are provided with an improved form of governor operating on the same principle, but embodying several important features. First, the spindle sleeve is integral with the governor yoke, and the whole rotates about a vertical stationary spindle, so that two motions are encountered—a rotary motion and an up and down motion, according to the position taken by the governor. This spiral motion almost entirely eliminates the effect of friction of rest, and thereby enhances the sensitiveness of the governor. Second, the governor weights move outward on a parallel motion opposed directly by spring thrust, thus relieving the fulcrum entirely of spring thrust. Third, the lay shaft driving the governor oil pump and reciprocator is located underneath the main turbine shaft, so that the rotor may be readily removed without in the least disturbing the governor adjustment.