An automatic watch, also known as a self-winding watch or simply an automatic, is a
mechanical watch
A mechanical watch is a watch that uses a clockwork mechanism to measure the passage of time, as opposed to quartz watches which function using the vibration modes of a piezoelectric quartz tuning fork, or radio watches, which are quartz watches ...
where the natural motion of the wearer provides energy to wind the
mainspring
A mainspring is a spiral torsion spring of metal ribbon—commonly spring steel—used as a power source in mechanical watches, some clocks, and other clockwork mechanisms. ''Winding'' the timepiece, by turning a knob or key, stores energy in ...
, making
manual winding
A mechanical watch is a watch that uses a clockwork mechanism to measure the passage of time, as opposed to quartz watches which function using the vibration modes of a piezoelectric quartz tuning fork, or radio watches, which are quartz watches ...
unnecessary if worn enough. It is distinguished from a ''manual watch'' in that a manual watch must have its mainspring wound by hand at regular intervals.
Operation
In a
mechanical watch
A mechanical watch is a watch that uses a clockwork mechanism to measure the passage of time, as opposed to quartz watches which function using the vibration modes of a piezoelectric quartz tuning fork, or radio watches, which are quartz watches ...
the watch's gears are turned by a spiral spring called a
mainspring
A mainspring is a spiral torsion spring of metal ribbon—commonly spring steel—used as a power source in mechanical watches, some clocks, and other clockwork mechanisms. ''Winding'' the timepiece, by turning a knob or key, stores energy in ...
. In a ''manual watch'' energy is stored in the mainspring by turning a knob, the ''crown'' on the side of the watch. Then the energy from the mainspring powers the watch movement until it runs down, requiring the spring to be wound again.
A self-winding watch movement has a mechanism which winds the mainspring using the natural motions of the wearer's body. The watch contains an oscillating weight that turns on a pivot. The normal movements of the watch in the user's pocket (for a
pocketwatch
A pocket watch (or pocketwatch) is a watch that is made to be carried in a pocket, as opposed to a wristwatch, which is strapped to the wrist.
They were the most common type of watch from their development in the 16th century until wristwatc ...
) or on the user's arm (for a
wristwatch
A watch is a portable timepiece intended to be carried or worn by a person. It is designed to keep a consistent movement despite the motions caused by the person's activities. A wristwatch is designed to be worn around the wrist, attached by ...
) cause the rotor to pivot on its staff, which is attached to a
ratchet
Ratchet may refer to:
Devices
* Ratchet (device), a mechanical device that allows movement in only one direction
* Ratchet, metonomic name for a socket wrench incorporating a ratcheting device
* Ratchet (instrument), a music instrument and a ...
ed winding mechanism. The motion of the watch is thereby translated into circular motion of the weight which, through a series of reverser and reducing gears, eventually winds the mainspring. There are many different designs for modern self-winding mechanisms. Some designs allow winding of the watch to take place while the weight swings in only one direction while other, more advanced, mechanisms have two ratchets and wind the mainspring during both clockwise and anti-clockwise weight motions.
The fully wound mainspring in a typical watch can store enough energy reserve for roughly two days, allowing the watch to keep running through the night while stationary. In many cases automatic wristwatches can also be wound manually by turning the crown, so the watch can be kept running when not worn, and in case the wearer's wrist motions are not sufficient to keep it wound automatically.
Preventing overwinding
Self-winding mechanisms continue working even after the mainspring is fully wound up. If a simple mainspring was used, this would put excessive tension on the mainspring. This could break the mainspring, and even if it did not, it can cause a problem called "knocking" or "banking". The excessive drive force applied to the watch movement gear train can make the
balance wheel
A balance wheel, or balance, is the timekeeping device used in mechanical watches and small clocks, analogous to the pendulum in a pendulum clock. It is a weighted wheel that rotates back and forth, being returned toward its center position by a ...
rotate with excessive amplitude, causing the impulse pin to hit the back of the
pallet fork
The pallet fork is a component of the lever escapement of a mechanical watch. The pallet fork and the lever form one component that sits between the escape wheel and the balance wheel. Its purpose is to lock the escape wheel, and release it one t ...
horns. This will make the watch run fast, and could break the impulse pin. To prevent this, a slipping clutch device is used on the mainspring so it cannot be overwound.
Slipping spring or "bridle"
The "slipping mainspring" device was patented by
Adrien Philippe
Jean Adrien Philippe (April 16, 1815, La Bazoche-Gouet, Eure-et-Loir – January 5, 1894) was a French horologist and cofounder of watchmaker Patek Philippe & Co. of Geneva, Switzerland.
In 1842, Adrien Philippe invented a mechanism for watches ...
, one of the founders of
Patek Philippe
Patek Philippe SA is a Swiss luxury watch and clock manufacturer, located in the Canton of Geneva and the Vallée de Joux. Established in 1839, it is named after two of its founders, Antoni Patek and Adrien Philippe. Since 1932, the company ha ...
, on 16 June 1863, long before self-winding wristwatches. In an ordinary watch mainspring
barrel
A barrel or cask is a hollow cylindrical container with a bulging center, longer than it is wide. They are traditionally made of wooden staves and bound by wooden or metal hoops. The word vat is often used for large containers for liquids, ...
, the outer end of the spiral mainspring is attached to the inside of the barrel. In the slipping barrel, the mainspring is attached to a circular steel expansion spring, often called the 'bridle', which presses against the inside wall of the barrel, which has serrations or notches to hold it.
As long as the mainspring is less than fully wound, the bridle holds the mainspring by friction to the barrel wall, allowing the mainspring to be wound. When the mainspring reaches full wind, its force is stronger than the bridle spring, and further winding pulls the bridle loose from the notches and it simply slides along the wall, preventing the mainspring from being wound further. The bridle must grip the barrel wall with just the right force to allow the mainspring to wind fully but not overwind. If it grips too loosely, the bridle will begin to slip before the mainspring is fully wound, a defect known as 'mainspring creep' which results in a shortened reserve power time.
A further advantage of this device is that the mainspring cannot be broken by excessive manual winding. This feature is often described in watch company advertising as an "unbreakable mainspring".
History
Pocket watches
![Mazzi-rotor](https://upload.wikimedia.org/wikipedia/commons/9/9c/Mazzi-rotor.jpg)
The earliest reference to self-winding watches is at the end of 1773 when a newspaper reported that Joseph Tlustos had invented a watch that did not need to be wound. But his idea was probably based on the myth of perpetual motion, and it is unlikely that it was a practical solution to the problem of self-winding watches. In 1776 Joseph Gallmayr also stated that he had made a self-winding watch, but there is no evidence to support this claim.
The earliest credible evidence for a successful design is the watch made by the Swiss watchmaker
Abraham-Louis Perrelet, who lived in Le Locle. In late 1776 or early 1777, he invented a self-winding mechanism for
pocket watch
A pocket watch (or pocketwatch) is a watch that is made to be carried in a pocket, as opposed to a watch, wristwatch, which is strapped to the wrist.
They were the most common type of watch from their development in the 16th century until wr ...
es using an oscillating weight inside the watch that moved up and down. The Geneva Society of Arts, reporting on this watch in 1777, stated that 15 minutes walking was necessary to fully wind the watch.
In 1777
Abraham-Louis Breguet
Abraham-Louis Breguet (10 January 1747 – 17 September 1823), born in Neuchâtel, then a Prussian principality, was a horologist who made many innovations in the course of a career in watchmaking industry. He was the founder of the Bregue ...
also became interested in the idea, and his first attempts led him to make a self-winding mechanism with a barrel
remontoire In mechanical horology, a remontoire (from the French ''remonter'', meaning 'to wind') is a small secondary source of power, a weight or spring, which runs the timekeeping mechanism and is itself periodically rewound by the timepiece's main power so ...
. Although a successful design, it was too complex and expensive for it to be manufactured and sold.
About the end of 1777 or early 1778, Hubert Sarton (
:fr: Hubert Sarton) designed a watch with a rotor mechanism. Towards the end of 1778 he sent a watch to the
French Academy of Sciences
The French Academy of Sciences (French: ''Académie des sciences'') is a learned society, founded in 1666 by Louis XIV of France, Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French Scientific me ...
and a report was written which, together with a drawing, gave a detailed description of the mechanism. Sarton's design is similar to those used in modern wrist watches, although there is no evidence linking the 18th-century design to 20th-century developments.
About the beginning of 1779, Abraham-Louis Breguet became aware of Perrelet's watches, probably through Louis Recordon, who travelled from Geneva to London via Le Locle and Paris. Breguet studied and improved the design, and made many self-winding watches from then to about 1810.
Although a few self-winding watches and patents for them were made from 1780 on, for more than one hundred years these watches were rare, until the advent of the wrist watch.
During the years 1776 to 1810 four different types of weight were used:
; Side-weight
: The weight pivots at the edge of the movement and can oscillate up and down. The movement of the weight is limited to about 40°. This is the most common design produced by many makers including Breguet.
: These watches were called ''jerking watches'' because, even with buffers, when the weight hit the case the whole watch would jerk.
; Center-weight
: The weight pivots in the center of the movement and rotates clockwise and anti-clockwise. The weight is supported by a bridge that blocks the rotation and it is limited to about 180°. A few movements were made by different makers.
; Rotor-weight
: Again the weight pivots in the center of the movement and rotates clockwise and anti-clockwise. However, there is no bridge and it can rotate 360°. Very few of these movements were made.
; Movement-weight
: Here the whole movement is pivoted in the case and acts as the weight. Only one example is known, made in 1806.
As noted above, some watches used bidirectional winding and others used unidirectional winding. The latter is sufficient and all of Breguet's watches used unidirectional winding.
Before the invention of the slipping mainspring, automatic watches had a system for locking the weight. Most common, as in the 1780 drawing, when the mainspring was fully wound a lever ''K'' was raised that entered a hole ''N'' in the weight to prevent it from moving until the mainspring had unwound enough to lower the lever. Different methods were used in side-weight, rotor and center-weight mechanisms.
Wrist watches
The advent of the wrist watch after World War I led to renewed interest in self-winding mechanisms, and all four types listed above were used:
* 1922: Léon Leroy, a side-weight system. This was almost certainly derived from Breguet's design.
* 1923: Harwood, a center-weight system (invented ca 1917). This is discussed below. It is not known if Harwood was influenced by earlier pocket watch designs.
* 1930: Léon Hatot, ''Rolls'' watch, where the whole movement moves sideways. This was probably an independent re-invention.
* 1931: Rolex, a rotor system with unidirectional winding.
Harwood "Bumper" wristwatches: 1923
![Automatic Watch](https://upload.wikimedia.org/wikipedia/commons/f/f2/Automatic_watch.jpg)
Invented by
John Harwood, a watch repairer from Bolton, England, who took out a UK patent with his financial backer, Harry Cutts, on 7 July 1923, and obtained a corresponding Swiss patent on 16 October 1923. The Harwood system used a pivoting weight which swung as the wearer moved, winding the mainspring. The ratchet mechanism wound the mainspring only when moving in one direction. The weight did not rotate a full 360°; spring bumpers limited its swing to about 180°, to encourage a back and forth motion. This early type of self-winding mechanism is now referred to as a 'hammer' or 'bumper'.
Like its 18th-century counterparts, Harwood's watch also had a problem with jerking because ''"the brass weight hit too sharply against the banking pins as it pivoted"''.
When fully wound, Harwood's watch would run for 12 hours autonomously. It did not have a conventional stem winder, so the hands were moved manually by rotating a bezel around the face of the watch. The watches were first produced with the help of Swiss watch manufacturer
Fortis and went on sale in 1928. 30,000 were made before the Harwood Self-Winding Watch Company collapsed in 1931 in the
Great Depression
The Great Depression (19291939) was an economic shock that impacted most countries across the world. It was a period of economic depression that became evident after a major fall in stock prices in the United States. The economic contagio ...
. 'Bumper' watches were the first commercially successful automatic watches; they were made by several high grade watch manufacturers during the 1930s and 1940s.
Rolex
The
Rolex
Rolex SA () is a British-founded Swiss watch designer and manufacturer based in Geneva, Switzerland. Founded in 1905 as ''Wilsdorf and Davis'' by Hans Wilsdorf and Alfred Davis in London, the company registered ''Rolex'' as the brand name of ...
Watch Company improved Harwood's design in 1930 and used it as the basis for the company's Oyster Perpetual, in which the centrally mounted semi-circular weight could rotate through a full 360° rather than the about 200° of the 'bumper' winder. Rolex's version also increased the amount of energy stored in the mainspring, allowing it to run autonomously for up to 35 hours.
Information about 18th-century rotor watches was not published until 1949. Although the Oyster Perpetual was probably an original invention, the company may have known of Coviot's 1893 patent that re-invented the 18th-century design.
Glycine and mass production of automatics
With John Harwood's patent for self-winding watches set to expire in the early 1930s,
Glycine
Glycine (symbol Gly or G; ) is an amino acid that has a single hydrogen atom as its side chain. It is the simplest stable amino acid (carbamic acid is unstable), with the chemical formula NH2‐ CH2‐ COOH. Glycine is one of the proteinogeni ...
founder Eugène Meylan started developing his own self-winding mechanism. Meylan’s design was unusual: a separate module that could be used with almost any 8.75 ligne (19.74 millimeter) watch movement. In October 1930, Glycine released their first automatic watches using this module, which became the world's first widely-produced automatic watches. This allowed Glycine to survive the global depression in the 1930s that caused many Swiss watchmakers to close shop.
Eterna ball bearing
The next development for automatic watches came in 1948 from
Eterna Watch. To wind a watch effectively, one of the chief requirements of a rotor is heft. Until this point, the best bearing used in any watch was a
jewel bearing
A jewel bearing is a plain bearing in which a metal spindle turns in a jewel-lined pivot hole. The hole is typically shaped like a torus and is slightly larger than the shaft diameter. The jewels are typically made from the mineral corundum ...
, which perfectly suits the small gears of a watch. A rotor, on the other hand, requires a different solution. In 1948, Eterna introduced the solution that is still in use today:
ball bearing
A ball bearing is a type of rolling-element bearing that uses balls to maintain the separation between the bearing races.
The purpose of a ball bearing is to reduce rotational friction and support radial and axial loads. It achieves this ...
s. Ball bearings provide robust support for a heavy object to rotate smoothly and reliably even under abnormal stress, such as if the watch were dropped. Eterna adopted geared bidirectional winding shortly afterwards.
Carl F. Bucherer weighted geared ring
![CFB A1000](https://upload.wikimedia.org/wikipedia/commons/a/a6/CFB_A1000.jpg)
By the 1960s, automatic winding had become widespread in quality mechanical watches. Because the rotor weight needed in an automatic watch takes up a lot of space in the case, increasing its thickness, some manufacturers of quality watches, such as
Patek Philippe
Patek Philippe SA is a Swiss luxury watch and clock manufacturer, located in the Canton of Geneva and the Vallée de Joux. Established in 1839, it is named after two of its founders, Antoni Patek and Adrien Philippe. Since 1932, the company ha ...
, continue to design manually wound watches, which can be as thin as 1.77 millimeters.
However, in 2007
Carl F. Bucherer
Carl F. Bucherer is a Swiss watch company based in Lucerne, Switzerland, which manufactures luxury men's and women's mechanical watches. From its founding in 1888 until its sale in 2023, the company was wholly owned by the Bucherer family, making ...
implemented a new approach without a rotor, a peripherally mounted power source, where a geared ring and a
rotating unbalance
Rotating unbalance is the uneven distribution of mass around an axis of rotation. A rotating mass, or rotor, is said to be out of balance when its center of mass (inertia axis) is out of alignment with the center of rotation (geometric axis). Unbal ...
mass segment made of
tungsten
Tungsten, or wolfram, is a chemical element with the symbol W and atomic number 74. Tungsten is a rare metal found naturally on Earth almost exclusively as compounds with other elements. It was identified as a new element in 1781 and first isolat ...
encircles the entire mechanism, rotating on carbon rollers whenever the watch moves. A system of clutch wheels captures power. No rotor means thinner watches and an ultradense weight swinging around a greater radius means a better chance of achieving a greater power reserve with same amount of arm movement.
See also
*
Automatic quartz
Automatic quartz is a collective term describing watch movements that combine a self-winding rotor mechanism (as used in automatic mechanical watches) to generate electricity with a piezoelectric quartz crystal as its timing element. Such mov ...
*
ETA movements
*
Jewel bearing
A jewel bearing is a plain bearing in which a metal spindle turns in a jewel-lined pivot hole. The hole is typically shaped like a torus and is slightly larger than the shaft diameter. The jewels are typically made from the mineral corundum ...
*
Miyota 8215
*
Regenerative brake
Regenerative braking is an energy recovery mechanism that slows down a moving vehicle or object by converting its kinetic energy into a form that can be either used immediately or stored until needed. In this mechanism, the electric traction mo ...
Explanatory notes
References
*
External links
A visual guide to the gears that make bi-directional winding possibleA detailed evaluation of the mechanics of the Seiko 7S26 automatic watch movement* Photos of early automatic movements on German watch vendor site, including the Harwood
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Energy harvesting
Transducers
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