FIELD: balance spring.
SUBSTANCE: present invention is related to a balance spring, in particular for a watch resonator mechanism, wherein the balance spring (1) contains a flexible strip (2) wound around itself in a plurality of turns, wherein the strip (2) has a given stiffness, wherein the spring (1 , 10, 20) of the balance contains a means for adjusting its rigidity, characterized in that the adjusting means contains a single elongated flexible element (5) located in series with the strip (2), and the elongated flexible element (5) connects one end (4, 9) of said strip (2) with a fixed support (11, 14) in such a way as to impart additional rigidity to the strip (2), wherein the elongated flexible element (5) preferably has a rigidity greater than that of the strip (2), wherein the adjusting means comprises pre-stressing means (6) for applying at least two different stresses to the elongated flexible member (5), wherein the first stress is generated by a tensile/compressive force FL directed substantially in the longitudinal direction of the elongated flexible member (5), and the second stress is generated either by a force FT directed in a direction substantially orthogonal to the longitudinal direction of the elongated flexible element (5), or by a torque M, preferably a bending moment, so as to change the stiffness of the elongated flexible element (5).
EFFECT: invention is also related to a watch resonator mechanism containing such balance spring (1).
15 cl, 5 dwg
