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The Encyclopedia of Horology

Switzerland · Rolex's 'Perpetual' rotor-winding system patented and introduced from 1931

Full-Rotor Automatic Winding Mechanism

Partially verified

The full-rotor architecture proved more efficient and durable than the bumper system and remains the basis of the great majority of automatic mechanical watches produced today.

Unlike Harwood's bumper mechanism, which swings a semicircular weight between two buffer springs, a full rotor turns freely through a complete 360-degree rotation in either direction, winding the mainspring via a reduction gear train regardless of the weight's swing direction.

Rolex marketed the mechanism as the 'Perpetual' and the free-rotating rotor architecture, refined over subsequent decades and copied (under licence or via independently developed equivalents) across the industry, became the dominant automatic-winding layout.

How to verify this yourself

Rolex's 1931 Swiss and corresponding foreign patent filings can be searched via Espacenet and the Swiss Federal Institute of Intellectual Property historical register under Rolex/Wilsdorf; exact publication numbers are not asserted here pending direct search.

Manufacturers known to have used it

  • Rolex
  • most subsequent Swiss, Japanese and other manufacturers of automatic mechanical watches

Related photographs

Watch automatic mainspring
Watch automatic mainspring — Hustvedt, CC BY-SA 3.0. 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. Rolex, published company history of the Oyster Perpetual mechanism
  2. Cutmore, M., Watches 1850–1980

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