Patent ID: 9239569
Filing Date: 2016-01-19
CPC Classification: G04B

Claim Text:
1. A balance spring, wherein said balance spring includes, in succession and forming a continuous band, from an upstream inner end, an inner coil of decreasing section, and wherein said balance spring includes, in succession, from an inner end and with angles at the center relative to an axial reference which are tangent to each other and all having a concavity facing said axial reference, and forming a continuous band: a first inner coil to a first point, at a first angle at the center and of decreasing section in a first ratio; a second coil to a second point, at a second angle at the center and of constant section; a third coil to a third point, at a third angle at the center and of increasing section in a third ratio; a fourth coil to a fourth point, at a fourth angle at the center and of constant section; a fifth coil to a fifth point, at a fifth angle at the center and of increasing section in a fifth ratio; a sixth outer coil to a sixth point, at a sixth angle at the center and of increasing section in a sixth ratio.