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The Encyclopedia of Horology

United States (Crane); Switzerland/France (Reutter, Atmos development) · Crane's patents c. 1840s–1850s; Reutter's Atmos-related work from the 1920s, industrialised by Jaeger-LeCoultre from 1936

Torsion Pendulum Clock Mechanism

Partially verified

Torsion clocks (including 400-day 'anniversary' clocks) and the Atmos in particular are notable for extremely low power consumption and, in the Atmos case, essentially self-winding operation from ambient temperature change.

A torsion pendulum clock replaces the swinging pendulum with a weighted disc suspended on a thin wire or ribbon that twists and untwists, giving a very low rate of energy loss and long running times between windings.

Reutter's version, combined with a sealed bellows mechanism responding to small changes in atmospheric temperature and pressure to rewind the mainspring, became the basis of the Atmos clock manufactured by Jaeger-LeCoultre.

How to verify this yourself

Crane's original US patents should be looked up by name and decade in the USPTO historical patent full-text/image database; Reutter's and Jaeger-LeCoultre's Atmos-related patents can be searched via Espacenet under 'Reutter' and 'Atmos' with 1920s–1930s date ranges.

Manufacturers known to have used it

  • Jaeger-LeCoultre (Atmos)
  • various 400-day anniversary clock manufacturers, chiefly German, 20th century

Related photographs

Pendule Atmos
Pendule Atmos — Tangopaso, CC BY-SA 3.0. Wikimedia Commons file page
Atmos clock prototype, Jaeger-LeCoultre - Karl Gebhardt Horological Collection - Gewerbemuseum - Nuremberg, Germany - DSC01841
Atmos clock prototype, Jaeger-LeCoultre - Karl Gebhardt Horological Collection - Gewerbemuseum - Nuremberg, Germany - DSC01841 — Daderot, CC0. Wikimedia Commons file page

No confidently matched photograph of this subject has been found yet. These photographs show a closely related record, and are not examples of the type described on this page.

Sources & references

  1. Jaeger-LeCoultre, published Atmos clock history
  2. USPTO historical archive (existence of Crane filings noted, numbers not independently verified here)

Where sources disagree, the disagreement is stated rather than resolved silently.