Spring e.g. barrel spring, for e.g. skeleton wrist watch, has core that is hollowed or made of material lighter than that of envelope, where contact surfaces between adjacent coils of spring is reduced to finite number of lines
The spring has a core (10) that is hollowed or made of a material lighter than material such as amorphous material or crystalline material, of an envelope (20), where the spring is formed by physical vapor deposition (PVD) or deep PVD. Section of the spring is such that contact surfaces between a coil (1) and an adjacent coil of the spring is reduced to a finite number of lines, where the section is in the form of a triangle, circle, ellipse, ovoid, polygon or multi- or flour-leaf clover. An independent claim is also included for a method for manufacturing a spring.
