Auto-compensating spring for mechanical oscillatory spiral spring of clockwork movement and method of manufacturing the same

摘要

The autocompensating hairspring is made from a paramagnetic alloy of. Niobium and Zirconium containing 5%-25% of. Zirconium by weight and having a thermal coefficient of. Young's. Modulus such that a function (1/E).(DE/DT) + 3 alpha s - 2 alpha b tends to zero, E being. Young's. Modulus, T the temperature, alpha s the thermal coefficient of expansion of the hairspring and alpha b the thermal coefficient of expansion of the balance wheel. The alloy should include at least 500 ppm by weight of a doping agent containing oxygen and is formed from wire by pressing or drawing in oxygen followed by cold working to form a ribbon. The ribbon is spiralled and heat treated at pressure to reduce the thermal coefficient of the Young's. Modulus by controlled precipitation of phases rich in. Zirconium.