=The Throttle= on an engine is the valve which allows the steam to
enter or be shut off from the cylinder and should always be left wide
open on a governor engine when running, as the governor regulates the
quantity of steam required to run it at its proper speed and is much
more economical.
There are different styles of valves used for throttles, such as Globe
Valves, Butterfly Valves, Disc Valves, etc.
[Illustration: Lunkenheimer Throttle Valve.]
The Lunkenheimer is a double disc valve, and is operated by the handle
or rod attachment, and requires no lock or ratchet.