Under the Loupe/Keyless Work
The term keyless work, originated in the middle of the 19th century when timepieces that could be set and wound without the need for a key or fob began to appear. Prior to this time, it was necessary for every clock or watch to have an accompanying key in order to function. When mechanisms were introduced, which eliminated this reliance on a key, the resulting timepieces were advertised as keyless watches. Thus, the mechanism responsible for this advent in horological technology became known as the keyless work.
Early examples of this type of mechanism were engineered to wind the mainspring only and not to set the time. A number of variations on the concept were produced in the years following, and the multi-function clutch and lever system utilized in the majority of watches today eventually prevailed.
In its simplest form today, the keyless work serves to wind and set a watch.
The principle of the keyless works is that a turnable knob on the outside of the case, called the crown, is fixed to a specially formed steel stem which facilitates the transfer of energy from the turning of the crown to the current state in which the clutch is engaged (winding or setting, et cetera).
In most single barrel watches, when engaged in the winding position, turning the button forward winds the watch, while turning it back does nothing. In watches with more than one barrel, such as clock watches or alarm watches, the mainspring of each is wound alternatively, in one direction and the other.
Generally, pulling the crown out to its furthest position engages the clutch with a series of gears which facilitate the setting of the time both forwards and backwards. Intermediate states between the winding and setting position can typically be found in watches with day, date, or other complications. Some types of complicated watches employ more than one crown - or multiple keyless works - to facilitate the setting and winding of multiple functions.
References
- Theory of Horology by Antoine Simonin et al ISBN 978-2940025121
- Old and Sold Antiques Digest ca. 1918