Watch hairspring and method for making same
AssigneeCSEM Centre Suisse d'Electronique et de Microtechnique SA
InventorsClaude Bourgeois, André Perret, Arnold Christiaan Hoogerwerf
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Abstract
The invention relates mainly to a hairspring intended to equip the balance wheel of a mechanical timepiece. It is in the form of a spiraled rod (10) cut from an {001} single-crystal silicon plate. Its structure and its dimensions are calculated so as to minimize the thermal drift of the hairspring/balance-wheel assembly by means of the first and second thermal coefficients of its spring constant.
Claims11
A new hairspring intended to equip the balance wheel of a mechanical timepiece and in the form of a spiraled rod (10) cut from an {001} single-crystal silicon plate having a first thermal coefficient (C1) and a second thermal coefficient (C2) of its spring constant C, the turns of said hairspring having a width w and a thickness t, characterized in that said rod comprises a silicon core (12) and an external layer (14) of thickness ξ formed around the silicon core and made of a material having a first thermal coefficient of the Young's modulus of opposite sign to that of the silicon.
Dependencies are inferred from the claim text.