IMPULSE

In watchmaking, the impulse is the action by which a force sets in movement, or sustains, an element. It is at the heart of the escapement, whose role is to periodically transmit to the oscillator the energy that compensates for losses due to friction. Concretely, a tooth of the escape wheel pushes the pallet stone of the pallets (lever) while resting on its impulse plane: the lever is thus propelled, then, through the fork and the impulse pin (roller jewel), it transmits to its lathe this impulse to the Balance, maintaining its Oscillation. Without this regular input, the balance-Hairspring (balance spring), like any real oscillator, would eventually stop due to friction. The quality of the impulse — its angle, its timing and the regularity of its transmission — determines the Amplitude of the balance and, therefore, the accuracy of the watch. Understanding the impulse, the rest, the Unlocking (drop angle) and the Drop (impact), means understanding the very functioning of the escapement, the energy-distributing organ of the timekeeper’s Time.

The mode of transmission of the Impulse distinguishes the major families of escapements. In the Swiss lever escapement, the Impulse is double: it occurs at each Vibration, on the Entry Pallet stone then on the exit Pallet stone, by sliding of the Escape wheel teeth on the inclined planes of the Pallet stones. The Detent escapement of marine chronometers, conversely, delivers only a single Impulse every two beats, through an almost parallel contact limiting friction, hence its reputation for precision, but also its fragility. The coaxial escapement, invented by George Daniels in 1976 and marketed by Omega from 1999, transmits the Impulse by radial rather than sliding friction, further reducing losses and Lubrication needs. To find out more: WOSTEP.