A balance-spring, particularly for a timepiece resonator mechanism. An adjustment device include a single elongated flexible element (5) arranged in series of strip (2), connecting one end (4, 9) of said strip (2) to a fixed support (11), to add an additional stiffness to the strip (2), and having a stiffness greater than that of the strip (2). A prestressing means (6) applies at least two different stresses on the elongated flexible element (5), the first stress being provided by a tensile/compressive force directed substantially in the longitudinal direction F.sub.L of the elongated flexible element (5), and the second stress being provided, either by a force directed substantially in a direction substantially orthogonal F.sub.T to the longitudinal direction of the elongated flexible element (5), or by a torque M, preferably a bending moment, in such a way as to vary the stiffness of the elongated flexible element (5).

A device for autonomous adjustment of the active length of a balance spring includes a regulator mounted on a plate with a cock, a balance spring stud holder being pivotally mounted on the cock, the regulator being pivotally mounted on the stud holder and including a pivot arm and device for changing the active length of the balance spring by pivoting the regulator. The device includes an elastic stress device to exert an elastic, return-to-position action on the regulator, and an inertia block, mounted for free rotation on the cock and connected to the pivot arm of the regulator, arranged to move the pivot arm of the regulator between a rest position and a correction position of the device, and simultaneously act on the device for changing the active length of the balance spring.

A spiral spring for a horological resonator mechanism, including a flexible strip (2) coiled on itself into several turns, the strip (2) having a predefined stiffness. The spring (1) include an element for adjusting its stiffness, including a unique elongate flexible element (5) arranged in series with the strip (2), and connecting one end (4) of said strip (2) to a fixed support (11), to add additional stiffness. The flexible element (5) has a stiffness higher than that of the strip (2). A prestressing element (6) applies two different efforts on the element (5), and includes a first lever (8) attached to the end (4) of the strip (2) to allow adjusting a first effort, and a second lever (8) also attached to the end (4) of the strip (2) to adjust a second effort independently of the first effort.

A spiral spring for a horological resonator mechanism, including a flexible strip (2) coiled on itself into several turns The spring (1) including an element for adjusting its stiffness, which includes a first elongate flexible element (5), and a second elongate flexible element (15) arranged in series with the strip (2), each elongate flexible element (5) connecting the same end (4) of the strip (2) to a fixed support (11), so as to add an additional stiffness to the strip (2), each elongate flexible element (5) preferably having a stiffness higher than that of the strip (2). A prestressing element (6) applies at least two different adjustable efforts, the two efforts being applied on the first elongate flexible element (5) so as to make the stiffness of the first elongate flexible element (5) vary according to the prestress level.

A device for autonomous adjustment of the active length of a balance spring includes a regulator mounted on a plate with a cock, a balance spring stud holder being pivotally mounted on the cock, the regulator being pivotally mounted on the stud holder and including a pivot arm and device for changing the active length of the balance spring by pivoting the regulator. The device includes an elastic stress device to exert an elastic, return-to-position action on the regulator, and an inertia block, mounted for free rotation on the cock and connected to the pivot arm of the regulator, arranged to move the pivot arm of the regulator between a rest position and a correction position of the device, and simultaneously act on the device for changing the active length of the balance spring.

A device (6) for autonomous adjustment of the active length of a spiral (5), for a balance-spiral type oscillator (4, 5), including a cock (12) mounted on a plate (13) of a horological movement (2) and in which a balance shaft pivots, the spiral (5) including an inner end secured to the balance shaft and an outer end secured to a balance spring stud (8) fastened to a balance spring stud holder (10), the balance spring stud holder (10) being pivotably mounted on the cock (12) concentrically with the balance shaft, and means for modifying the active length of the spiral (5).

A device (6) for autonomously adjusting the active length of a balance spring (5), for an oscillator (4, 5) of the sprung balance type, including a cock (12) mounted on a plate (13) of a horological movement (2) and in which cock a balance staff pivots, the balance spring (5) including an inner end integral with the balance staff and an outer end integral with a first stud (8) fastened to a stud-holder (10), the stud-holder (10) being pivotally mounted on the cock (12) concentrically with the balance staff, and means for modifying the active length of the balance spring (5).

A device (6) for autonomous adjustment of the active length of a spiral (5), for oscillators (4, 5) of the balance-spiral type, comprising a cock (12) mounted on a plate (13) of a horological movement (2) and in which a balance shaft pivots, the spiral (5) including an inner end secured to the balance shaft and an outer end secured to a balance spring stud (8) fastened to a balance spring stud holder (10), the balance spring stud holder (10) being pivotably mounted on the cock (12) concentrically to the balance shaft, and means for modifying the active length of the spiral (5).

A device (6) for autonomously adjusting the active length of a balance spring (5), for an oscillator (4, 5) of the sprung balance type, including a cock (12) mounted on a plate (13) of a horological movement (2) and in which cock a balance staff pivots, the balance spring (5) including an inner end integral with the balance staff and an outer end integral with a stud (8) fastened to a stud-holder (10), the stud-holder (10) being pivotally mounted on the cock (12) concentrically with the balance staff, and means for modifying the active length of the balance spring (5).

A horological assembly for a horological regulating member, including a balance spring (25) having a coiled flexible strip (2); a device for adjusting its rigidity which includes a flexible element (5) arranged in series with the strip and connecting one end (4) of said strip to a rigid support (17), the flexible element having a rigidity greater than that of the strip. The adjustment device includes a pre-stressing device (6) for applying a variable force or torque to the flexible element to vary the rigidity of the flexible element. A stud-holder (1) is configured to suspend the balance spring and includes a main body (30) connected to the flexible element, and a secondary body (33) connected to the pre-stressing device, the secondary body (33) being movable relative to the main body (30) and being connected to the main body by a flexure bearing (20).