Mechanisms
Escapement Encyclopedia
The escapement is where a timekeeper counts. Each design below is recorded with its working principle, the period and place it belongs to, what it does well, what it does badly, and the watches and clocks in which it is found. Attributions of invention are given as attributions, because most are contested.
3 records
Frictional rest escapements
Frictional restVerge (crown-wheel) escapementTwo pallets on a vertical verge staff alternately engage the teeth of a horizontally mounted crown wheel, giving impulse and recoil on every vibration.c. 1300 in clocks; adapted to watches by the sixteenth centuryFrictional restCylinder (horizontal) escapementRaised escape-wheel teeth enter a cut-away cylinder on the balance staff, impulsing on entry and exit while resting against the cylinder wall between.Early eighteenth century, associated with George Graham
Frictional restDuplex escapementA single escape wheel carries two sets of teeth — long locking teeth and short impulse teeth — delivering one impulse per two vibrations to a roller on the balance staff.Eighteenth century; refined in England and later used in American production6 records
Detached escapements
DetachedLever escapementA pivoted lever with two jewelled pallets locks the escape wheel and transmits impulse to the balance through a fork and impulse pin, leaving the balance detached for most of its arc.Attributed to Thomas Mudge, c. 1754; developed through the nineteenth century
DetachedDetent (chronometer) escapementA spring or pivoted detent locks the escape wheel; the balance unlocks it once per revolution and receives a single direct impulse, remaining otherwise entirely free.Late eighteenth century, associated with Earnshaw and Arnold
DetachedPin-pallet (pin-lever) escapementSteel pins set into the pallet arms engage the escape-wheel teeth directly in place of jewelled pallet stones, giving a simplified and cheaper version of the lever escapement's locking and impulse action.Developed in the nineteenth century and widely adopted for inexpensive watches and clocks from the early twentieth centuryDetachedEnglish (right-angle) lever escapementThe pallet fork and balance-roller impulse jewel are arranged at a right angle to the line joining the escape wheel and pallets, generally combined with a ratchet-tooth escape wheel; the layout descends directly from English fusee-watch practice.Developed through the early nineteenth century from Thomas Mudge's original leverDetachedSwiss (straight-line) lever escapementEscape wheel, pallet fork pivot and balance staff are arranged on a single straight line, typically with a club-tooth escape wheel; the compact layout suits thin, going-barrel movements built for volume production.Standardised through the nineteenth century as Continental going-barrel production matured5 records
Clock escapements
ClockGraham deadbeat escapementPallets with concentric locking faces hold the escape wheel motionless during the pendulum's excursion, eliminating recoil.c. 1715, George Graham
ClockRecoil (anchor) escapementAn anchor-shaped pallet engages the escape wheel so that, at each half-vibration, the wheel is briefly driven backwards ('recoils') before locking again, which allows the pendulum to swing through a wide arc while remaining connected to the train.c. 1670s, generally attributed to Robert Hooke and associated with William Clement's clocks
ClockGravity escapementGravity arms are alternately raised by the clock train and then released to fall against the pendulum, delivering an impulse of almost constant force regardless of variation in the train's driving torque or friction.Nineteenth century; the double three-legged form is associated with Edmund Beckett Denison (Lord Grimthorpe) and was used for the Great Clock at the Palace of Westminster
ClockGrasshopper escapementA pair of pallets pivoted so that they swing almost clear of the escape wheel and of each other, giving impulse to the pendulum with very little frictional contact and, in Harrison's own view, no need for lubrication.c. 1722, John HarrisonClockBrocot (visible) deadbeat escapementA deadbeat-type escapement in which the pallets are jewelled and mounted visibly at the dial centre, behind pierced apertures, so the escapement's action can be watched; functionally it behaves as a standard deadbeat escapement.Mid-nineteenth century, associated with the Parisian maker Achille Brocot