Since the driving escape wheel tooth moves almost parallel to the pallet and in one direction only, the escapement has little friction and need no oiling.įor these reasons, the detent demonstrated to be the most accurate escapement for balance wheel timepieces keeping time to within 1 or 2 seconds per day, an accuracy which approaches that of a modern quartz watch. But while the lever escapement gives two impulses per cycle, the detent escapement gives just one impulse per cycle (every other swing) interfering with the balance as little as possible.ĭrawing from “The Marine Chronometer, its history and development” by Rupert Gould (London, 1923) Like the lever escapement, the detent escapement is a detached escapement, allowing the balance wheel to swing undisturbed during most of its cycle, except for the brief impulse period. In the late 18th century British watchmakers John Arnold (1736-1799) and Thomas Earnshaw (1749-1829) developed their own versions of detent escapements.Įarnshaw's design was the simplest possible and demonstrated to be the most efficient and reliable establishing itself as the reference and most deployed detent escapement. Originally invented by Pierre Le Roy (1717–1785) in 1748, in the following years it was modified and further developed by other watchmakers. The escape wheel has specially shaped teeth which interact with the two jewels called the entrance and exit pallets.Īnimation of a Swiss lever escapement - Courtesy of Mark Headrick and īut there is an escapement that can guarantee a much higher precision. The rotation of the escape wheel is controlled by the pallets. This type of escapement offers two main advantages: 1) the balance wheel is only in contact with the lever during the short impulse period (detached escapement) so reducing friction and improving accuracy, and 2) it is a self-starting escapement, so if the balance wheel stops, a delicate twist will be sufficient to restart it. Invented by British watchmaker Thomas Mudge (1715-1794) in 1750, it has been used in the vast majority of watches since the 19th century.
The most popular escapement is the so-called in-line or Swiss lever escapement. Without the escapement, the spring would unwind in a few seconds making the wheel turn too fast, just like a coil spring that, compressed between two fingers, is released suddenly.
This regular periodic advancement moves the clock's hands forward at a steady rate. In particular, each swing of the balance wheel releases a tooth of the escapement's escape wheel gear, allowing the clock's gear train to advance or "escape" by a fixed amount. An escapement is a device in mechanical watches that transforms the energy from the unwinding of a coiled spring (the power source) into countable impulses.
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