1798 - Constant force escapement
Breguet patented this invention on March 9, 1798 (19 Ventôse, Year 6, in the Republican calendar). Its basic principle is the exchange of the motive power that supplies the movement of a watch, which may be irregular in its effect, with another, strictly constant force. In the solution described in his patent, the watch parts’ variable output is used to push up a spring or weight, which provides a constant impulse to the oscillating part. Intriguing in theory but extremely delicate in practice, the constant-force escapement was used by Breguet only in a few rare and prestigious pieces.
Water-colour illustration for the constant-force escapement patent, filed in 1798. Institut national de la propriété industrielle, Paris