Escapement

detent escapementCross-beat escapementduplex escapementsspring detent escapementacted as a large gearclock escapement mechanismdeadbeat escapementdouble comma escapementescapement with constant forceescapements
An escapement is a mechanical linkage in mechanical watches and clocks that gives impulses to the timekeeping element and periodically releases the gear train to move forward, advancing the clock's hands.wikipedia
218 Related Articles

Mechanical watch

mechanicalmechanical watchesmanual winding
An escapement is a mechanical linkage in mechanical watches and clocks that gives impulses to the timekeeping element and periodically releases the gear train to move forward, advancing the clock's hands.
A device called an escapement releases the watch's wheels to move forward a small amount with each swing of the balance wheel, moving the watch's hands forward at a constant rate.

Balance wheel

foliotbalancecompensation balance
The impulse action transfers energy to the clock's timekeeping element (usually a pendulum or balance wheel) to replace the energy lost to friction during its cycle and keep the timekeeper oscillating.
It is driven by the escapement, which transforms the rotating motion of the watch gear train into impulses delivered to the balance wheel.

Clock

timepiecemechanical clockanalog clock
An escapement is a mechanical linkage in mechanical watches and clocks that gives impulses to the timekeeping element and periodically releases the gear train to move forward, advancing the clock's hands. The importance of the escapement in the history of technology is that it was the key invention that made the all-mechanical clock possible.
Arab engineers at the time also developed a liquid-driven escapement mechanism which they employed in some of their water clocks.

Water clock

clepsydrawater clockswater-clock
The invention of the first all-mechanical escapement, the verge escapement, in 13th-century Europe initiated a change in timekeeping methods from continuous processes, such as the flow of water in water clocks, to repetitive oscillatory processes, such as the swing of pendulums, which could yield more accuracy.
The Greeks and Romans advanced water clock design to include the inflow clepsydra with an early feedback system, gearing, and escapement mechanism, which were connected to fanciful automata and resulted in improved accuracy.

Pendulum

pendulumssimple pendulumpendula
The impulse action transfers energy to the clock's timekeeping element (usually a pendulum or balance wheel) to replace the energy lost to friction during its cycle and keep the timekeeper oscillating. The invention of the first all-mechanical escapement, the verge escapement, in 13th-century Europe initiated a change in timekeeping methods from continuous processes, such as the flow of water in water clocks, to repetitive oscillatory processes, such as the swing of pendulums, which could yield more accuracy.
The crutch is pushed back and forth by the clock's escapement, (g,h) .

Yi Xing

Xing, YiZhang Sui
In China, the Tang dynasty Buddhist monk Yi Xing along with government official Liang Lingzan made the escapement in 723 (or 725) to the workings of a water-powered armillary sphere and clock drive, which was the world's first clockwork escapement.
His astronomical celestial globe featured a clockwork escapement mechanism, the first in a long tradition of Chinese astronomical clockworks.

Astronomical clock

astronomicalastronomical clock towerastronomical clock towers
late 10th century) and Su Song (1020–1101) duly applied escapement devices for their astronomical clock towers, before the technology stagnated and retrogressed.
Su Song is noted for having incorporated an escapement mechanism and earliest known endless power-transmitting chain drive for his clock-tower and armillary sphere to function.

Su Song

Su SungEndless power-transmitting chain driveSong, Su
late 10th century) and Su Song (1020–1101) duly applied escapement devices for their astronomical clock towers, before the technology stagnated and retrogressed.
Su Song was the engineer for a hydro-mechanical astronomical clock tower in medieval Kaifeng, which employed the use of an early escapement mechanism.

Verge escapement

verge and foliotfoliotcrown wheel and verge escapement
The invention of the first all-mechanical escapement, the verge escapement, in 13th-century Europe initiated a change in timekeeping methods from continuous processes, such as the flow of water in water clocks, to repetitive oscillatory processes, such as the swing of pendulums, which could yield more accuracy. The first mechanical escapement, the verge escapement, was invented in medieval Europe during the 13th century, and was the crucial innovation which lead to the development of the mechanical clock.
The verge (or crown wheel) escapement is the earliest known type of mechanical escapement, the mechanism in a mechanical clock that controls its rate by allowing the gear train to advance at regular intervals or 'ticks'.

History of technology

historian of technologytechnologytechnological growth
The importance of the escapement in the history of technology is that it was the key invention that made the all-mechanical clock possible.
In time-keeping, the introduction of the inflow clepsydra and its mechanization by the dial and pointer, the application of a feedback system and the escapement mechanism far superseded the earlier outflow clepsydra.

Armillary sphere

armillaryarmillary spheresArmil
In China, the Tang dynasty Buddhist monk Yi Xing along with government official Liang Lingzan made the escapement in 723 (or 725) to the workings of a water-powered armillary sphere and clock drive, which was the world's first clockwork escapement.
In 723 AD, Yi Xing and government official Liang Ling-zan combined Zhang Heng's water powered celestial globe with an escapement device.

Grasshopper escapement

Some escapements avoid sliding friction; examples include the grasshopper escapement of John Harrison in the 18th century, This may avoid the need for lubrication in the escapement (though it does not obviate the requirement for lubrication of other parts of the gear train).
The grasshopper escapement is a low-friction escapement for pendulum clocks invented by British clockmaker John Harrison around 1722.

Washstand

washbasins
The earliest liquid-driven escapement was described by the Greek engineer Philo of Byzantium (3rd century BC) in his technical treatise Pneumatics (chapter 31) as part of a washstand.
In his Pneumatics, (chapter 31) Philo of Byzantium, a Greek engineer and writer on mechanics, describes an escapement mechanism, the earliest known, as part of a washstand.

Zhang Sixun

Song dynasty (960–1279) horologists Zhang Sixun (fl.
The liquid mercury filled scoops of the waterwheel would rotate and thus provide the effect of an escapement mechanism in clockworks and allow the astronomical armillary sphere to rotate as needed.

Clockwork

clockwork motorclockworksClockwork Doll
Historically, a liquid-driven escapement was used for a washstand design in ancient Greece and the Hellenistic world, particularly Ptolemaic Egypt, while liquid-driven escapements were applied to clockworks beginning in Tang dynasty China and culminating during the Song dynasty.
Often power for the device is stored within it, via a winding device that applies mechanical stress to an energy-storage mechanism such as a mainspring, thus involving some form of escapement; in other cases, hand power may be utilized.

Tourbillon

tourbillion
The tourbillon was invented to minimize this: the balance and spring is put in a cage which rotates (typically but not necessarily, once a minute), smoothing gravitational distortions.
In horology, a tourbillon ( "whirlwind") is an addition to the mechanics of a watch escapement.

Song dynasty

SongSouthern Song dynastyNorthern Song dynasty
Song dynasty (960–1279) horologists Zhang Sixun (fl. Historically, a liquid-driven escapement was used for a washstand design in ancient Greece and the Hellenistic world, particularly Ptolemaic Egypt, while liquid-driven escapements were applied to clockworks beginning in Tang dynasty China and culminating during the Song dynasty.
The clock tower featured large astronomical instruments of the armillary sphere and celestial globe, both driven by an early intermittently working escapement mechanism (similarly to the western verge escapement of true mechanical clocks appeared in medieval clockworks, derived from ancient clockworks of classical times).

Tang dynasty

TangTang ChinaTang Empire
In China, the Tang dynasty Buddhist monk Yi Xing along with government official Liang Lingzan made the escapement in 723 (or 725) to the workings of a water-powered armillary sphere and clock drive, which was the world's first clockwork escapement. Historically, a liquid-driven escapement was used for a washstand design in ancient Greece and the Hellenistic world, particularly Ptolemaic Egypt, while liquid-driven escapements were applied to clockworks beginning in Tang dynasty China and culminating during the Song dynasty.
3rd century), which gave the Tang mathematician, mechanical engineer, astronomer, and monk Yi Xing (683–727) inspiration when he invented the world's first clockwork escapement mechanism in 725.

Anchor escapement

deadbeat escapementdeadbeatGraham escapement
These problems were eliminated in the deadbeat escapement, which slowly replaced the anchor in precision clocks.
In horology, the anchor escapement is a type of escapement used in pendulum clocks.

John Harrison

H-4H4H4 and H5
Some escapements avoid sliding friction; examples include the grasshopper escapement of John Harrison in the 18th century, This may avoid the need for lubrication in the escapement (though it does not obviate the requirement for lubrication of other parts of the gear train).
In the 1720s, the English clockmaker Henry Sully invented a marine clock that was designed to determine longitude: this was in the form of a clock with a large balance wheel that was vertically mounted on friction rollers and impulsed by a frictional rest Debaufre type escapement.

Philo of Byzantium

Philon of ByzantiumPhilo
The earliest liquid-driven escapement was described by the Greek engineer Philo of Byzantium (3rd century BC) in his technical treatise Pneumatics (chapter 31) as part of a washstand.
In his Pneumatics (chapter 31) Philo describes an escapement mechanism, the earliest known, as part of a washstand.

Lever escapement

escapement wheelLeverlever escapements
Therefore, the self-starting lever escapement became dominant in watches.
The lever escapement, invented by British clockmaker Thomas Mudge in 1755, 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.

Remontoire

However, this improvement was probably not due to the escapement itself, but rather to better workmanship and his invention of the remontoire, a device which isolated the escapement from changes in drive force.
It was used in precision clocks and watches to place the source of power closer to the escapement, thereby increasing the accuracy by evening out variations in drive force caused by unevenness of the friction in the geartrain.

John Arnold (watchmaker)

John ArnoldJohn Roger ArnoldJohn Arnold (1736–1799)
The first effective design of detent escapement was invented by John Arnold around 1775, but with the detent pivoted.
Around 1780, Earnshaw modified his detent escapement by mounting the detent on a spring to create the spring detent escapement.

Thomas Earnshaw

Earnshaw
This escapement was modified by Thomas Earnshaw in 1780 and patented by Wright (for whom he worked) in 1783; however, as depicted in the patent it was unworkable.
He is also known for his improvements to the transit clock at the Royal Greenwich Observatory in London and his invention of a chronometer escapement and a form of bimetallic compensation balance.