The cylinder escapement is a watch escapement that uses a cut-away cylinder on the balance shaft in place of pallets. Thomas Tompion devised it in 1695. It allowed much slimmer watches than the verge and needed no fusee. From 1750 on, it was the most widely used escapement.
How does a cylinder escapement work?
The balance shaft carries a small cylinder with part of its wall cut away. The teeth of the escape wheel pass into this cylinder one at a time. Each tooth is shaped like a wedge. As a tooth goes in, it presses on the edge of the cylinder, and that pressure pushes the balance. This push is called impulse. A typical cylinder escape wheel had fifteen teeth. It gave the balance impulse over 20 to 40 degrees each way.
Where it comes from
The design is credited to Thomas Tompion. George Graham later refined Tompion’s design and brought it to its developed form in 1726. Early cylinders had one serious weakness: they wore badly. That mattered in a part that the escape-wheel teeth touch all the time. The French solved the problem by making both the cylinder and the escape wheel from hardened steel.
How is it different from the lever escapement?
The cylinder is a frictional rest escapement. The escape-wheel teeth touch the cylinder throughout the balance’s whole cycle, not only when they give impulse. Between pushes, a tooth rests against the cylinder as the balance turns. The lever escapement works differently. There, the balance swings freely for most of its arc. That constant contact is what sets the cylinder apart from the lever.
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