Movement for use in timepiece i.e. watch, has magnetic polarization device to maintain predefined polarization state in hairspring of hairspring-balance resonator to make movement less variable after exposure to external magnetic field

摘要

The movement (1) has a hairspring-balance resonator (3) mounted between a bridge (2) and a plate (4) and comprising a hairspring (7) made of ferromagnetic material. A magnetic polarization device (15) of the hairspring maintains a predefined polarization state in the hairspring to make the movement less variable after an exposure to an external magnetic field. The polarization device has a permanent magnetization unit (17) to generate a field equal to three times the corrective force of material of the hairspring.