An escapement is the linkage in a mechanical watch or clock that delivers pushes to the part that keeps time. It lets the gear train advance in regular steps, and those steps move the hands forward. Its power comes from a wound spring or a hanging weight.
How does an escapement work in a watch?
In a watch, the escape wheel is usually steel. The other wheels in the gear train are brass. Next to the escape wheel sits the pallet fork. It is shaped like an anchor and is usually made of brass plated with nickel. The balance swings to keep time. Each time its roller jewel passes through the notch in the fork, it gets a push of energy. That keeps the balance running. Meanwhile the gear train moves forward one regular step at a time, and the hands move with it.
Where it comes from
The verge was the first fully mechanical escapement. It was created in Europe in the 1200s. Earlier still, in China, an escapement was built in 723 or 725 AD. It ran an armillary sphere powered by water. The anchor escapement, credited to Robert Hooke around 1657, soon replaced the verge. In 1750 Thomas Mudge created the lever escapement. Most watches have used it since the 1800s. Almost every mechanical pocket watch and wristwatch made so far uses his detached lever. The co-axial is one of very few new watch escapements to reach commercial use in recent times.
What other types of escapement are there?
Escapements differ in how much they touch the balance. The detent escapement is a detached design. Its balance wheel swings freely for most of each cycle. Mudge’s lever is detached too. The cylinder escapement works differently. Its teeth rub against the cylinder throughout the balance wheel’s whole swing. Escapements have also been used outside timekeeping. In manual typewriters, one moved the carriage a single step for each keystroke.
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