STEAM ENGINES 387 



Principle of the throttling governor. Fig. 272 is a 

 sectional view of a throttling governor. The governor is 

 generally placed upon the steam chest, and when not in 

 this place it must be as close to it as possible. 



Steam enters the governor from the boiler through 

 the pipe A. Passing through the governor valve B, it 

 enters the steam chest C. If the valve B is clear up, 

 which is analogous to wide open, the steam passes into 

 the steam chest unmolested as far as pressure is con- 

 cerned, but if the valve B is partly closed the steam is 

 throttled as it passes the valve. Consequently the pres- 

 sure in the steam chest is not as great as in the steam 

 pipe A. From this it is seen that the only requisite for 

 a governor, other than the design of valve B, is some 

 device which will raise and lower the valve B as the 

 speed of the engine increases or decreases. 



The pulley D is run by a belt from the engine shaft, 

 and whenever the speed of the engine varies the speed 

 of this pulley also varies. By means of the beveled 

 pinions E and F the motion is transmitted from the 

 pulley D to the governor balls G and H. With no motion 

 in the pulley D these balls hang down, but as soon as the 

 pulley commences to revolve the balls do likewise, and, 

 due to centrifugal force, they commence to rise. When 

 the engine attains its full speed the balls, acting through 

 the arms / and / and valve rod, should have partly 

 closed the valve. By having the valve partly closed when 

 the engine is running at its normal speed there is oppor- 

 tunity for the valve to be opened when the speed drops. 

 If the engine is not carrying full load it will be inclined 

 to run too fast. This increased speed of the engine 

 causes the governor balls to rise higher and consequently 

 close the valve a trifle. It will be noticed that the gov- 

 ernor balls are not only acting on the valve D, but are 



