thumb|Inline or Swiss lever escapement (blue) and balance wheel (yellow)

thumb|Animation of inline lever escapement, showing motion of the lever (blue), pallets (red), and escape wheel (yellow)

thumb|A lever escapement in a mechanical watch. The largest brass<!--colour; not sure about material--> circle is the balance wheel. The escape wheel is the silver gear above and to the right of it whose bearing is surrounded by decorative engraving. Most of the lever itself is hidden, but both pallets are visible.

The lever escapement, invented by the English clockmaker Thomas Mudge in 1754 (albeit first used in 1769), is a type of escapement that is used in almost all mechanical watches, as well as small mechanical non-pendulum clocks, alarm clocks, and kitchen timers.

An escapement is a mechanical linkage that delivers impulses to the timepiece's balance wheel, keeping it oscillating back and forth, and with each swing of the balance wheel allows the timepiece's gear train to advance a fixed amount, thus moving the hands forward at a steady rate. The escapement is what makes the "ticking" sound in mechanical watches and clocks.

Invention

The lever escapement was invented by British clockmaker Thomas Mudge around 1754, and improved by Abraham-Louis Breguet (1787), Peter Litherland (1791), and Edward Massey (1800). Its modern ("table roller") form was developed by George Savage in the early 1800s. A problem with the lever escapement is friction. The escape wheel tooth slides along the face of the pallet, causing friction, so the pallets and teeth must be lubricated. The oil eventually thickens, causing inaccuracy, and requiring cleaning and reoiling of the movement about every 4 years. A solution is to make the escape wheel and other parts out of harder materials than steel, eliminating the need for lubrication. Materials being tried include silicon, nickel phosphorus, diamond, and diamond-on-silicon. Ulysse Nardin in 2001, Patek Philippe in 2005, and Zenith in 2013 introduced watches with silicon escape wheels.

See also

  • Anchor escapement
  • Co-axial escapement

References

  • An Analysis of the Lever Escapement, by H. R. Playtner, 1910, from Project Gutenberg