France (origin); England (Tyrer's patented refinement) · Origin c. 1720s–1750s (contested); Thomas Tyrer patented an English form in 1782
Duplex Escapement
Partially verifiedValued for accuracy at reasonable cost, the duplex escapement was widely used in mid-tier English watches and extensively in watches made for the Chinese export market before the lever escapement's cost fell enough to displace it.
The duplex escapement uses an escape wheel with two sets of teeth — long teeth for locking and short teeth for impulse — acting on a single roller on the balance staff, giving a largely detached action without the lever's added parts.
Tyrer's 1782 English patent is the most concretely documented milestone in the escapement's development, though the underlying French-attributed concept predates it by several decades according to horological historians.
Background
Jean Baptiste Dutertre and Pierre Le Roy improved the duplex escapement during its early development. The mechanism was brought into its final form by Thomas Tyrer, who secured an English patent for the invention in 1782. Designed to provide a high level of accuracy, the duplex escapement functions as a frictional-rest escapement that offers performance levels comparable to the early lever escapement. The mechanism utilizes an escape wheel equipped with two distinct sets of teeth to manage the locking and impulse phases of the cycle.
The balance wheel receives an impulse only during one of the two swings within its oscillation cycle. During operation, the locking teeth rest against a ruby disk, while the impulse tooth engages with a roller notch to provide the necessary force to the balance. This design minimizes sliding friction during the impulse phase by allowing the pallet and impulse tooth to move in an almost parallel fashion, reducing the requirement for constant lubrication.
Written from the encyclopedia entries listed under Sources; each statement was checked against the cited text.
How it works
- The escape wheel possesses long teeth intended for locking and short, axially oriented teeth for providing impulse.
- The escapement relies on a ruby roller and disk to interface with the locking and impulse teeth of the escape wheel.
Later history
- The escapement eventually lost favor because its extreme sensitivity to shock and tight tolerances made watches unsuitable for active use.
Where sources differ
- Inventor / attribution. This record gives: “Attributed to Jean Baptiste Dutertre (or Pierre Le Roy, priority contested); English development chiefly by Thomas Tyrer”. The cited history says the duplex escapement was invented by Robert Hooke around 1700, then improved by Dutertre and Le Roy.
How to verify this yourself
Tyrer's 1782 patent should be sought in The National Archives (Kew) historical patent enrolment series under his name; earlier French-attributed origins rest on horological-history literature rather than a surviving patent and should be cited as attribution, not as a documented filing.
Manufacturers known to have used it
- English watchmakers, late 18th–19th centuries
- Swiss export houses supplying the China trade
Photographs
Photographs are illustrative examples of the type, not necessarily the exact object described. Verify details against the source file page.
Sources & references
- Escapement, Wikipedia (English), retrieved 2026-10-28 (text CC BY-SA 4.0)
- Britten, F. J., Old Clocks and Watches and Their Makers
- The National Archives, Kew — patent enrolment index (existence of Tyrer's filing noted, number not independently verified here)
Where sources disagree, the disagreement is stated rather than resolved silently.