Fig. 3320.
The safety stop or stop motion is shown on the right, [Fig. 3320].
Fig. 3321.
It acts to close the governor valve and stop the engine in case the belt that drives the governor should get off the pulley or break. This stop motion consists of a pulley suspended by a rod, and riding on the belt which supports its weight. Should the governor belt break, this pulley falls and severs the connection between the valve and the governor, closing the valve, and holding it closed. [Fig. 3321] shows the governor in section to expose the construction of the valve. The valve v is what is termed a poppet or poppet valve, which is balanced, because the steam entering at i, and taking the course denoted by the arrows, acts equally on both ends of the valve and does not press it in either direction, while as the steam surrounds the valve it is not pressed sideways.
At b is a gland or stuffing box to keep the spindle or rod steam-tight. At a is the slot for receiving the arm from the speeder and from the stop motion.
p is obviously the driving pulley, imparting motion to the bevel wheels g, which drive the outer spindle s, the inner spindle s′ being connected to a. The balls are upon ribbon springs d, which are secured at their lower ends to a link fast to the spindle s.