REMONTOIR D’ÉGALITÉ (Constant-force escapement)
Remontoir d’égalité or constant-force escapement is a complication designed to deliver consistent energy to a watch movement, ensuring optimal precision. By enabling the regular distribution of energy stored in the mainspring, it compensates for fluctuations in the amplitude of the regulating organ caused by the gradual depletion of energy as the mainspring unwinds.
History and Origins
Remontoir d’égalité was developed in the 18th century. Comparable systems had already been utilised in some monumental clocks, where specific mechanisms required substantial bursts of energy to operate.
During this period, watchmakers sought to improve the stability and precision of mechanical timepieces. Chronometrically, the foundational idea was to counteract the effects of the diminishing energy in the mainspring, which negatively impacts the regulating organ.
The accuracy of mechanical watches varies depending on the residual energy within the barrel. As the mainspring unwinds, the driving force it transmits to the gear train and the regulating organ diminishes, disrupting the balance of the movement. The invention of the constant-force remontoir aimed to solve this issue by delivering a steady and regular amount of energy to the mechanism, regardless of the mainspring’s tension level.
Developed in the 18th century, this complication is closely tied to the pursuit of precision required for navigation (marine chronometers, Longitude Act).
Operating Principles
Remontoir d’égalité operates on the principle of consistently distributing energy to the movement, independent of the gradual depletion of energy in the mainspring. This is achieved via an additional mechanical device that regulates the energy supplied to the main mechanism.
The remontoir typically comprises two distinct springs:
- The mainspring: This primary spring provides the basic energy to drive the watch movement. It is traditionally wound manually or automatically, depending on the type of watch.
- The constant-force spring: The ingenuity of the remontoir lies here. This smaller spring, housed within a separate mechanism, is periodically wound by the mainspring and redistributes a consistent amount of energy to the movement, thereby regulating the force applied to the balance wheel.
The constant-force spring operates on a principle of continuous rewinding, releasing stable and regular energy at each interval, compensating for fluctuations from the mainspring.
The Regulation Mechanism
Another critical component of the remontoir is its transmission mechanism, which ensures that energy released by the remontoir spring is delivered to the primary movement at controlled and regular intervals. This can involve levers or gears that redistribute a consistent force, typically at the escapement level or occasionally upstream in the movement. The mechanism must transmit energy efficiently, minimising friction and its own energy consumption to preserve the effects of the constant-force system.
The Advantage of the Complication
The key feature of the remontoir d’égalité is its ability to supply consistent energy to the movement. This regulation of driving force reduces the effects of amplitude variations that usually occur as the mainspring tension weakens. Consequently, watches equipped with this complication demonstrate superior stability, particularly in terms of chronometric precision, throughout their operating duration.
Constructions and Innovations
While the foundational principles of the remontoir d’égalité have remained largely unchanged since its inception, numerous variations exist. It is distinct from fusée mechanisms, which solely utilise the mainspring’s energy. Innovations have focused on reducing the mechanism’s size or improving its performance, primarily through advancements in materials and manufacturing technologies, such as silicon and electroforming.
Conclusions
Remontoir d’égalité represents one of the most ingenious solutions for ensuring the consistent and precise regulation of energy in a mechanical movement. By enabling the watch to operate with regular driving force, this mechanism mitigates variations in precision, affirming its position as a hallmark of horological excellence.