Getting Technical: Swiss Lever Escapement
It was back in the mid-18th century that an ingenious English horologist named Thomas Mudge first invented the lever escapement at his workshop in Fleet Street. This invention was perhaps the greatest improvement to have ever been applied to watchmaking, and over the next century, several Swiss manufactures dedicated themselves to the improvement of this mechanical wonder. This refined version, that would become known in the 19th century as the Swiss lever escapement, is used to this day in the majority of mechanical watches—but how exactly does it work?
It is to the escapement that we owe the familiar ticking sound of a working mechanical timepiece—the beating heart of the watch, it stops the mainspring from releasing all of its energy at once. It is made up of a balance wheel, hairspring, pallet fork and escape wheel, and at the same time controls the release of energy from the mainspring, as well as ensuring that the balance assembly is kept going at a rate as steady and regular as possible.
Using the power released from the wound mainspring, the escape wheel moves in regulated steps, locking and unlocking the pallet fork as it moves. The teeth of the escape wheel push against the pallet fork’s entrance pallet with every movement, which is connected to a lever that ends in a fork shape.
As this fork is moved by the escape wheel, it hits a balance pin which forces the balance wheel to swing back and forth. As the balance wheel returns to its central position, it once again moves the pallet fork, which in turn causes the exit pallet to lock the escape wheel in place.
This process is repeated over and over again, with the continual movement of the balance wheel—kept in motion by the balance spring—causing a regular locking and unlocking of the escape wheel, regulating the release of power from the mainspring to the rest of the movement.
The advantages of this type of escapement are the improved accuracy in timekeeping, as well as the ‘self-starting’ nature of the mechanism, which means that if any accidental knocks or jars to the watch stop the balance wheel, it will start again on its own.
Watchmaking is all about innovation and improvement, and over the years, other escapements—such as co-axial movements—have been developed by enterprising watchmakers. The lever escapement, however, will remain a critical turning point in horological history.
Still scratching your head? Never fear! It’s a mechanism much easier to understand when seen in action—the video above gives a simple demonstration of how the Swiss lever escapement works.
