Improved spiral spring and method for manufacturing said spiral spring

摘要

The balance spring (2) is formed by a spiral bar (1) formed by a fused quartz core that is locally covered with an outer layer having a modified structure to modify the thermal coefficient of rigidity. The outer layer is made with the fused quartz at the core, the morphology of which has been modified by exposure to a femtosecond laser. Independent claims are also included for the following: (1) a balance spring-balance assembly; and (2) a method of manufacturing a balance spring.