Patent ID: 8414185

Claim:
A mechanical oscillator for watchmaking, the mechanical oscillator comprising: a spiral spring ( 1 ) having a number N of turns, a central end ( 2 ), an eccentric end ( 3 ), and a rotary collet ( 4 ) connected to the central end ( 2 ), the rotary collet defining an orifice that is capable of receiving an arbor for rotation about an axis (A), said spiral spring ( 1 ) being made up of a single-crystal silicon (Si) core ( 1 a ) and at least one peripheral coating ( 1 b ) having a thermoelastic coefficient different from that of silicon; and a balance ( 7 ), the axis of rotation of which coincides with axis (A), wherein the single-crystal silicon (Si) is cut along the crystallographic axis {1,1,1} and the spiral spring has a dimension that is selected based on the temperature coefficient of the mechanical oscillator.