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Anchor escapement

Animation showing operation of an anchor escapement
The anchor and escape wheel of a late 19th-century clock. The plate that normally holds the front end of the pinions has been removed for clarity. The pendulum is behind the back plate.

In horology, the anchor escapement is a type of escapement used in pendulum clocks. The escapement is a mechanism in a mechanical clock that maintains the swing of the pendulum by giving it a small push each swing, and allows the clock's wheels to advance a fixed amount with each swing, moving the clock's hands forward. The anchor escapement was so named because one of its principal parts is shaped vaguely like a ship's anchor.

The anchor escapement was invented by clockmaker William Clement,[1] [2][3] who popularized the anchor in his invention of the longcase or grandfather clock around 1680. Clement's invention was a substantial improvement on Robert Hooke's constant force escapement of 1671.[4] The oldest known anchor clock is Wadham College Clock, a tower clock built at Wadham College, Oxford, in 1670, probably by clockmaker Joseph Knibb.[5][6] The anchor became the standard escapement used in almost all pendulum clocks.

A more accurate variation without recoil called the deadbeat escapement was invented by Richard Towneley around 1675 and introduced by British clockmaker George Graham around 1715. This gradually superseded the ordinary anchor escapement and is used in most modern pendulum clocks.

  1. ^ Reid, Thomas (1832). Treatise on Clock and Watch-making, Theoretical and Practical. Philadelphia, USA: Carey & Lea. p. 184.
  2. ^ Beckett, Edmund (Lord Grimsthorpe) (1874). A Rudimentary Treatise on Clocks and Watches and Bells, 6th Ed. London: Lockwood & Co. p. 71.
  3. ^ Usher, Abbott Payson (1988). A History of Mechanical Inventions. Courier Dover. p. 313. ISBN 0-486-25593-X.
  4. ^ Inwood, Stephen (2003). The Forgotten Genius. San Francisco: MacAdam/Cage Pub. p. 34. ISBN 978-1-931561-56-3. OCLC 53006741. the oft-repeated claim that Hooke invented the anchor escapement originated in William Derham's The artificial clock-maker (1696), not with Hooke, and is now regarded as untrue.
  5. ^ Chapman, Allen (2005). England's Leonardo: Robert Hooke and the Seventeenth Century Scientific Revolution. CRC Press. p. 84. ISBN 0-7503-0987-3.
  6. ^ Macey, Samuel L., ed. (1994). Encyclopedia of Time. New York: Garland Publishing. p. 125. ISBN 0815306156.

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