Hairspring for timepiece resonator mechanism provided with means for adjusting the stiffness

Abstract

The invention relates to a spiral spring, particularly for a resonator mechanism in watchmaking, the spiral spring (1) comprising a flexible ribbon (2) wound upon itself in several turns, the ribbon (2) having a predefined stiffness, the spiral spring (1) comprising means for adjusting its stiffness, the adjustment means comprising a single elongated flexible element (5) arranged in series with the ribbon (2), the elongated flexible element (5) connecting one end (4) of said ribbon (2) to a fixed support (11), so as to add additional stiffness to the ribbon (2), the elongated flexible element (5) preferably having a stiffness greater than that of the ribbon (2), the adjustment means comprising preload means (6) for applying at least two different forces on the elongated flexible element (5), the preload means (6) comprising a first lever (8) attached to the end (4) of the ribbon (2) for being able to adjust a first force,The preload means (6) include a second lever (8) also attached to the end (4) of the ribbon (2) to allow for adjusting a second force independently of the first force. The invention also relates to a clockwork resonator mechanism comprising such a balance spring (1).

Description

Technical field of the invention

[0001] The invention relates to a balance spring for a resonator mechanism in watchmaking, the balance spring being equipped with means for adjusting its stiffness. The invention also relates to a resonator mechanism in watchmaking equipped with such a balance spring. Technological background

[0002] Most modern mechanical watches feature a balance wheel and hairspring, and a Swiss lever escapement mechanism. The balance wheel and hairspring form the watch's timekeeping base. It is also called a resonator.

[0003] The exhaust system, for its part, fulfills two main functions: to maintain the back-and-forth movement of the resonator; to count these back-and-forth movements.

[0004] To construct a mechanical resonator, one needs an inertial element, a guide, and an elastic return element. Traditionally, a spiral spring acts as the elastic return element for the inertial element, which is a balance wheel. This balance wheel is guided in rotation by pivots that rotate in ruby ​​plain bearings.

[0005] The balance spring must generally be adjustable to improve a watch's accuracy. To this end, methods are used to adjust the spring's stiffness, such as a regulator to modify its effective length. This alters its stiffness, thus adjusting the watch's accuracy. However, the effectiveness of a traditional regulator for adjusting the watch's rate remains limited, and it is not always sufficient to achieve a precision of a few seconds or tens of seconds per day.

[0006] For finer adjustment of the rate, there are adjustment mechanisms consisting of one or more screws arranged in the rim of the balance wheel. By adjusting the screws, the inertia of the balance wheel is modified, which in turn alters its rate.

[0007] However, this method of adjustment is not easy to perform, as it disturbs the balance of the balance wheel, and still does not allow for a sufficiently fine adjustment of the oscillator's rate.

[0008] Document EP 4 009 115 A1 shows a spiral spring with a first lever attached to the end of the ribbon to allow adjustment of a first force. Summary of the invention

[0009] The aim of the present invention is to overcome all or part of the aforementioned disadvantages, by proposing a spiral spring equipped with effective and precise adjustment means, configured in particular to regulate the rate of a timepiece by modifying the effective stiffness of said spiral.

[0010] For this purpose, the invention relates to a spiral spring, in particular for a resonator mechanism in watchmaking, the spiral spring comprising a flexible ribbon wound around itself in several turns, the ribbon having a predefined stiffness, the spiral spring comprising means for adjusting its stiffness, the adjustment means comprising a single elongated flexible element arranged in series with the ribbon, the elongated flexible element connecting one end of said ribbon to a fixed support, so as to add additional stiffness to the ribbon, the adjustment means comprising pre-stressing means for applying at least two different forces on the elongated flexible element.

[0011] The invention is remarkable in that the prestressing means include a first lever attached to the end of the ribbon to be able to adjust a first force, the prestressing means including a second lever also attached to the end of the ribbon to be able to adjust a second force independently of the first force.

[0012] Thanks to this invention, the stiffness of an elongated flexible element, such as a flexible blade, can be modified. Indeed, by applying two forces, the stiffness of the elongated flexible element can be varied. With a single applied force, whether a force or a torque, the stiffness of the elongated flexible element remains the same. With two perpendicular forces applied to the blade, longitudinally and orthogonally, a combined force is obtained, which changes the stiffness of the elongated flexible element. Applying both a force and a torque also modifies the stiffness. The combination of two forces is essential to modify the stiffness.

[0013] By adjusting the prestressing devices, the intensity of the stress is modulated, resulting in a change in the stiffness of the assembly comprising the flexible element and the ribbon. Indeed, the flexible element, when connected in series with the ribbon, provides additional stiffness, which combines with that of the ribbon. Thus, when the prestressing devices apply varying forces to the flexible element, they modify the stiffness of the flexible element and therefore of the assembly comprising the ribbon and the flexible element, without altering the stiffness of the ribbon itself, regardless of the varying forces applied to the elongated flexible element.

[0014] In other words, a flexible element is placed in series with the ribbon between one end of the ribbon and the fixed support. This flexible element provides additional adjustable stiffness between the ribbon and its attachment point, thus providing extra flexibility to the resonator. Therefore, the effective stiffness of the resonator comprises the stiffness of the ribbon and the stiffness of the flexible element. Variable forces are then applied to pre-stress the flexible element, preferably without pre-stressing the ribbon. By pre-stressing the flexible element, its stiffness changes, while the stiffness of the ribbon remains essentially unchanged. By changing the stiffness of the flexible element, the stiffness of the resonator (ribbon stiffness and flexible element stiffness) changes, which consequently alters the resonator's behavior.

[0015] Therefore, changing the stiffness of the flexible element alters the stiffness of the entire resonator, and consequently fine-tunes its performance, allowing for precise adjustment of the timebase frequency. This results in highly accurate timing, as only one additional element is used to fine-tune the stiffness of the spiral spring.

[0016] Furthermore, each of the two levers allows for independent preload adjustment, resulting in a more precise setting. Additionally, if the levers are different in shape, two different preload settings are possible.

[0017] According to a particular embodiment of the invention, the first effort is provided either by a first tensile / compressive force directed substantially in the longitudinal direction of the elongated flexible element, or by a first force directed substantially in a direction substantially orthogonal to the longitudinal direction of the elongated flexible element, or by a first couple, preferably a bending moment, so as to vary the stiffness of the elongated flexible element according to the level of prestress.

[0018] According to a particular embodiment of the invention, the second effort is provided either by a second tensile / compressive force directed substantially in the longitudinal direction of the elongated flexible element, or by a second force directed substantially in a direction substantially orthogonal to the longitudinal direction of the elongated flexible element, or by a second couple, preferably a bending moment, so as to vary the stiffness of the elongated flexible element according to the level of prestress.

[0019] According to a particular embodiment of the invention, the prestressing means are configured to exert a third force on the elongated flexible element, the third force being provided, respectively to the first force, either by a force directed substantially in a direction substantially orthogonal to the longitudinal direction of the elongated flexible element, or by a couple, preferably a bending moment.

[0020] According to a particular embodiment of the invention, the prestressing means are configured to exert a third force on the elongated flexible element, the third force being supplied, respectively to the first force, either by the first tensile / compressive force, or by the first substantially orthogonal force, or by the first torque. According to a particular embodiment of the invention, the third force is adjustable by the first lever.

[0021] According to a particular embodiment of the invention, the third effort is adjustable by the first lever.

[0022] According to a particular embodiment of the invention, the prestressing means are configured to exert a fourth force on the elongated flexible element, the fourth force being provided, respectively to the second force, either by the second tensile / compressive force, or by the second substantially orthogonal force, or by the second couple.

[0023] According to a particular embodiment of the invention, the fourth effort is adjustable by the second lever.

[0024] According to a particular embodiment of the invention, the prestressing means are configured to exert a fifth force on the elongated flexible element, the fifth force being provided, respectively to the first force and the third force, either by the first tensile / compressive force, or by the first substantially orthogonal force, or by the first couple.

[0025] According to a particular embodiment of the invention, the fifth effort is adjustable by the first lever.

[0026] According to a particular embodiment of the invention, the prestressing means are configured to exert a sixth force on the elongated flexible element, the sixth force being provided, respectively to the second and fourth forces, either by the second tensile / compressive force, or by the second substantially orthogonal force, or by the second couple.

[0027] According to a particular embodiment of the invention, the sixth effort is adjustable by the second lever.

[0028] According to a particular embodiment of the invention, the longitudinal flexible element is a single flexible blade.

[0029] According to a particular embodiment of the invention, the flexible element is arranged in a radial direction of the spiral spring.

[0030] According to a particular embodiment of the invention, the first and second levers are flexible.

[0031] According to a particular embodiment of the invention, the first and second are curved and at least partially surround the wound ribbon.

[0032] According to a particular embodiment of the invention, the first and second levers comprise a first free end actuable by a displacement of said first free end in order to apply said forces on the elongated flexible element.

[0033] According to a particular embodiment of the invention, the second lever includes a second free end actuable by a displacement of said second free end in order to apply said forces on the elongated flexible element.

[0034] According to a particular embodiment of the invention, the end of the ribbon comprises an appendage, the prestressing means and the elongated flexible element being joined to the appendage.

[0035] According to a particular embodiment of the invention, the longitudinal force(s), and possibly the torque, are continuously adjustable by means of prestressing.

[0036] According to a particular embodiment of the invention, the flexible element is arranged at an external end of the ribbon.

[0037] According to a particular embodiment of the invention, the end of the ribbon is more rigid than the elongated flexible element and the ribbon.

[0038] According to a particular embodiment of the invention, the elongated flexible element and the levers are arranged at an external end of the ribbon.

[0039] According to a particular embodiment of the invention, the elongated flexible element comprises a flexible neck.

[0040] According to a particular embodiment of the invention, the first and second levers are configured to allow adjustment of the force(s) to different intensities.

[0041] According to a particular embodiment of the invention, the first and second levers have a different stiffness or cross-section from each other.

[0042] The invention also relates to a rotary resonator mechanism, in particular for a watch movement, comprising an oscillating mass and such a balance spring. Brief description of the figures :

[0043] The aims, advantages and features of the present invention will become apparent from the reading of several embodiments given solely by way of non-limiting examples, with reference to the accompanying drawings in which: there figure 1 schematically represents a top view of a spiral spring according to one embodiment of the invention, and the figure 2 schematically represents an enlarged top view of the appendix and the forces applied to the appendix according to the first embodiment of the invention. Detailed description of the invention

[0044] There figure 1This shows a schematic representation of one embodiment of a balance spring 1, particularly for a resonator mechanism in a watch. Here, the balance spring 1 extends substantially in the same plane. The balance spring 1 comprises a flexible ribbon 2 wound around itself in several turns, the ribbon 2 having a predefined stiffness. The balance spring 1 includes means for adjusting its stiffness. For example, the adjustment means can be operated when the balance spring 1 is mounted on a plate of a watch movement, not shown in the figures.

[0045] According to the invention, the adjustment means comprise an elongated flexible element 5 extending longitudinally, which is arranged in series with the ribbon 2, the flexible element 5 connecting one end 4 of said ribbon 2 to a fixed support 11. In other words, the ribbon 2 is connected to the fixed support 11 only by this flexible element 5.

[0046] The flexible element 5 is attached to one of the ends 4 of the ribbon 2. The embodiments described below include a flexible element 5 attached to the outer end 4 of the ribbon 2. The inner end 19 of the ribbon 2 is intended to be assembled to a support 3 of an oscillating mass of the resonator 1.

[0047] The flexible element 5 adds additional stiffness to that of the ribbon 2. The flexible element 5 preferably has a stiffness greater than that of the ribbon 2. The flexible element 5 is arranged here in the extension of the ribbon 2. Preferably, the adjustment means 5 and the ribbon 2 are monoblocs, or even formed from the same material.

[0048] Furthermore, the end of the ribbon 2 is bent perpendicularly to form an appendage 9. This appendage serves as an attachment point and allows it to receive forces. It is preferably substantially rigid, that is, at least more rigid than the ribbon 2 and / or the elongated flexible element 5, to minimize its influence on the stiffness of the ribbon 2.

[0049] Preferably, the longitudinal flexible element 5 is a single flexible blade 13, 15 connecting the appendage 9 to the fixed support 11, 14.

[0050] The single flexible blade 13 is arranged in line with appendix 9. The single flexible blade 13 is arranged in a direction perpendicular to the end of ribbon 2.

[0051] Thus, the unique flexible blade 13 is arranged in a radial direction, preferably passing through the center of the spiral spring 1, in the rest position of the spiral spring 1.

[0052] The spiral spring 1 further includes prestressing means 6 for applying at least two different forces on the flexible element 5, a first force and a second force.

[0053] The first effort is provided either by an initial tensile / compressive force directed substantially in the longitudinal direction F L 1 of the elongated flexible element, either by a first force directed substantially in a substantially orthogonal direction F T 1 to the longitudinal direction of the elongated flexible element, either by a first couple M 1, preferably a bending moment, so as to vary the stiffness of the elongated flexible element according to the level of prestress.

[0054] The second effort is provided either by a second tensile / compressive force directed substantially in the longitudinal direction F L2 of the elongated flexible element, either by a second force directed substantially in a substantially orthogonal direction F T 2 to the longitudinal direction of the elongated flexible element 5, either by a second couple M 2, preferably a bending moment, so as to vary the stiffness of the elongated flexible element according to the level of prestress.

[0055] In this embodiment, the first strong point is the first longitudinal force. F L 1. Tension-compression, and the second effort is the second orthogonal force F T 2 , which are variable. The two forces preferably belong to the plane of the balance spring 1. Thus, the stiffness of the balance spring 1 can be finely adjusted, in particular to improve the accuracy of the movement's operation.

[0056] The prestressing means 6 allow the flexible element 5 to undergo a compressive or tensile force depending on the magnitude of the forces. This varies the stiffness of the flexible element 5.

[0057] Only the flexible element 5 is adjusted to modify its stiffness, without directly affecting the ribbon 2. This results in even greater precision, as only one element is used to adjust the stiffness. During oscillations, the end 4 of the ribbon 2 can be movable.

[0058] Furthermore, efforts, such as longitudinal forces F L 1, F L 2 and orthogonal F T 1 , F T 2 , are continuously adjustable by means of prestressing 6. In other words, the forces are not restricted to discrete values. Thus, the stiffness of the flexible element 5 can be adjusted with high precision.

[0059] The prestressing means 6 comprise a first lever 8 joined to the outer end 4 of the ribbon 2. The first lever 8 is curved and surrounds a portion of the wound ribbon 2. The first lever 8 has the shape of a semicircle, or an arc of a circle with a central angle close to 180°, joined to the appendage 9 of the end 4 of the ribbon 2.

[0060] The first lever 8 further includes a first free end 12 that can be actuated by a displacement of said first free end 12, in order to apply said forces. The first lever 8 is preferably flexible. The first free end 12 is arranged opposite the appendage 9. The first lever 8 is preferably arranged in the plane of the spiral spring 1. The first lever 8 thus allows adjustment of the first force.

[0061] The prestressing means 6 include a second lever 15 joined to the outer end 4 of the ribbon 2. The second lever 15 is curved and surrounds a part of the wound ribbon 2, preferably on the other side of the ribbon 2 relative to the first lever 8. The second lever 15 has the shape of a semicircle, or an arc of a circle with a center angle close to 90°, joined to the appendage 9 of the end 4 of the ribbon 2.

[0062] The second lever 15 further includes a second free end 16 actuated by a displacement of said first free end 16, in order to apply said forces. The second free end 16 is arranged opposite appendage 9.

[0063] The second lever 16 is preferably flexible. The second lever 15 is preferably arranged in the plane of the spiral spring 1. The second lever 15 thus allows adjustment of the second force. Therefore, the first 8 and the second lever 15 meet and are joined to the same appendage 9 of the curved part of the end 4 of the ribbon 2.

[0064] The first lever 8 allows adjustment of the first force, while the second lever 15 allows adjustment of the second force. Thus, the two forces are adjustable independently of each other.

[0065] The prestressing means 6 are preferably configured to exert other forces on the elongated flexible element 5 by means of the first 8 and the second lever 15. Each lever 8, 15 preferably exerts several forces, independently of each other, here three forces simultaneously.

[0066] The prestressing means 6 are configured to exert a third force on the elongated flexible element. This third force is supplied, respectively, by the first tensile / compressive force. F L 1, either by the first substantially orthogonal force F T 1 , either by the first couple M 1. In this embodiment, the third effort is the first substantially orthogonal force. F T 1 . The third effort is adjustable using the first lever 8.

[0067] Thus, the first lever 8 allows the first and third effort to be adjusted simultaneously.

[0068] The prestressing means 6 are further configured to exert a fourth force on the elongated flexible element 5, the fourth force being supplied, respectively to the second force, by the second tensile / compressive force FL 1, or by the second force substantially orthogonal F T 2 , either by the second couple M 2. In this embodiment, the fourth effort is the second substantially longitudinal force. F L 2. The fourth effort is adjustable using the second lever 15.

[0069] The prestressing means 6 are further configured to exert a fifth force on the elongated flexible element 5, the fifth force being supplied, respectively to the first and third forces, by the first tensile / compressive force. F L 1, either by the first substantially orthogonal force F T 1 , either by the first couple M 1.

[0070] In this implementation mode, the fifth effort is the first couple M1. The fifth effort is adjustable via the first lever 8. The fifth effort is adjustable by the first lever 8.

[0071] The prestressing means 6 are also configured to exert a sixth force on the elongated flexible element 5, the sixth force being supplied, respectively to the second and fourth forces, by the second tensile / compressive force. F L 2, or by the second force substantially orthogonal F T 2 , either by the second couple M 2. In this embodiment, the sixth effort is the second torque M 2. The sixth effort is adjustable by the second lever 15.

[0072] In this embodiment, the forces produced by each lever 8, 15 are opposed, except for the longitudinal forces. F L 1 , F L2 which have the same direction. However, the first 8 and the second lever 15 have a similar effect on the stiffness of the elongated flexible element 5. The higher a lever 8, 15 is raised, the more the stiffness of the elongated flexible element 5 increases.

[0073] Each lever allows the stiffness of the elongated flexible element 5 to be changed individually, as it provides at least two forces.

[0074] Preferably, the first lever (8) and the second lever (18) are configured to allow adjustment of the forces they apply at different intensities. Thus, one lever allows adjustment within a wider range, and the other lever allows adjustment within a finer range.

[0075] To obtain a difference in the intensity of adjustment of the stiffness of the elongated flexible element 5 between the two levers 8, 15, the section of the two levers 8, 15 is for example chosen to be different, or the stiffness of each lever 8, 15 is chosen to be different.

[0076] Thus, the forces or torques applied are less with a smaller section or stiffness than with a larger section or stiffness, so that the two levers 8, 15 allow the stiffness of the elongated flexible element 5 to be modified on two different scales.

[0077] Such levers 8, 15 allow a balance spring 1 to be kept with a reduced size, the dimensions being restricted so that it can be inserted into a watch movement.

[0078] Indeed, the prestressing means 6 have a shape that matches the ribbon 2, so as to maintain sufficiently small dimensions, since each part of the prestressing means 6 is close to the ribbon 2. The width of the spiral spring 1 is therefore only slightly modified by the prestressing means. Thus, the spiral spring 1 is compact enough to be easily incorporated into a movement.

[0079] As shown by figure 2 , the actuation of the first lever 8 produces on the end 4 of the ribbon 2 the longitudinal force F L 1 directed along the longitudinal axis of the flexible longitudinal element 5, as well as an orthogonal force F T 1 directed along an orthogonal direction. The actuation of the first lever 8 also produces a bending torque or moment M 1 on the single blade 5, represented by a curved arrow.

[0080] Activating the second lever 15 produces the longitudinal force F L 2 directed in the same direction as the longitudinal force F L 1, the orthogonal force F T 2 directed in the opposite direction to the orthogonal force F T 1, and a couple M 2 in the opposite direction of the couple M 1.

[0081] Thus, the stiffness of the single blade 13 is modified, and therefore of the assembly comprising the ribbon 2 and the single flexible blade 13.

[0082] We vary the longitudinal forces F L 1, F L 2 and orthogonal F T 1, F T 2 as well as couples M 1, M2. This is achieved by moving the first free end 12 of the first lever 8 and the second free end 16 of the second lever 15. The first 12 and the second free end 16 are preferably rigid to facilitate their actuation. Thus, the stiffness of the flexible element 5, and therefore of the assembly comprising the flexible element 5 and the ribbon 2, is varied.

[0083] The invention also relates to a clockwork movement comprising such a balance spring 1. The balance spring is notably used to drive the movement of a balance wheel.

[0084] Naturally, the invention is not limited to the embodiments described with reference to the figures and variants could be envisaged without departing from the scope of the invention.

[0085] Regarding the longitudinal element, the flexible blades described in the different embodiments of the spiral spring can be continuous flexible blades, as is generally the case in the figures, or blades with rigid sections and flexible necks connecting the sections.

[0086] Furthermore, the single flexible blade can assume orientations other than radial and orthogonal to the spiral spring. Thus, it can be oriented along any direction between radial and orthogonal.

Claims

1. A spiral spring, in particular for a horological resonator mechanism, the spiral spring (1) comprising a flexible strip (2) coiled on itself into several turns, the strip (2) having a predefined stiffness, the spiral spring (1) including means for adjusting its stiffness, the adjustment means including a unique elongate flexible element (5) arranged in series with the strip (2), the elongate flexible element (5) connecting one end (4, 19) of said strip (2) to a fixed support (11), so as to add an additional stiffness to the strip (2), the elongate flexible element (5) preferably having a stiffness higher than that of the strip (2), the adjustment means including prestressing means (6) to apply at least two different efforts on the elongate flexible element (5), the prestressing means (6) including a first lever (8) attached to the end (4, 19) of the strip (2) so as to allow adjusting a first effort, characterised in that the prestressing means (6) include a second lever (8) also attached to the end (4, 19) of the strip (2) so as to be able to adjust a second effort independently of the first effort.

2. The spiral spring according to claim 1, characterised in that the first effort is imparted, either by a first tensile / compressive force directed substantially in the longitudinal direction FL1 of the elongate flexible element (5), or by a first force directed substantially in a direction substantially orthogonal FT1 to the longitudinal direction of the elongate flexible element (5), or by a first torque M1, preferably a bending moment, so as to make the stiffness of the elongate flexible element (5) vary according to the prestress level.

3. The spiral spring according to claim 1 or 2, characterised in that the second effort is imparted either by a second tensile / compressive force directed substantially in the longitudinal direction FL2 of the elongate flexible element (5), or by a second force directed substantially in a direction substantially orthogonal FT2 to the longitudinal direction of the elongate flexible element (5), or by a second torque M2, preferably a bending moment, so as to make the stiffness of the elongate flexible element (5) vary according to the prestress level.

4. The spiral spring according to any one of the preceding claims, characterised in that the prestressing means (6) are configured to exert a third effort on the elongate flexible element (5), the third effort being imparted, respectively at the first effort, either by the first tensile / compressive force FL1, or by the substantially orthogonal first force FT1, or by the first torque M1.

5. The spiral spring according to claim 4, characterised in that the third effort is adjustable by the first lever (8).

6. The spiral spring according to any one of the preceding claims, when they depend of claims 3,characterised in that the prestressing means (6) are configured to exert a fourth effort on the elongate flexible element (5), the fourth effort being imparted, respectively at the second effort, either by the second tensile / compressive force FL2, or by the substantially orthogonal second force FT2, or by the second torque M2.

7. The spiral spring according to claim 6, characterised in that the fourth effort is adjustable by the second lever (15).

8. The spiral spring according to any one of the preceding claims, when they depend of claims 2 and 4, characterised in that the prestressing means (6) are configured to exert a fifth effort on the elongate flexible element (5), the fifth effort being imparted, respectively at the first effort and at the third effort, either by the first tensile / compressive force FL1, or by the substantially orthogonal first force FT1, or by the first torque M1.

9. The spiral spring according to claim 8, characterised in that the fifth effort is adjustable by the first lever (8).

10. The spiral spring according to any one of the preceding claims, , when they depend of claims 3 and 6, characterised in that the prestressing means (6) are configured to exert a sixth effort on the elongate flexible element (5), the sixth effort being imparted, respectively to the second effort and at the fourth effort, either by the second tensile / compressive force FL2, or by the substantially orthogonal second force FT2, or by the second torque M2.

11. The spiral spring according to claim 10, characterised in that the sixth effort is adjustable by the second lever (15).

12. The spiral spring according to any one of the preceding claims, characterised in that the elongate flexible element (5) is a unique flexible blade (13).

13. The spiral spring according to any one of the preceding claims, characterised in that the flexible element (5) is arranged in a radial direction of the spiral spring (1).

14. The spiral spring according to any one of the preceding claims, characterised in that the first (8) and second (15) levers are flexible.

15. The spiral spring according to any one of the preceding claims, characterised in that the first lever (8) comprises a first free end (12) which can be actuated by a movement of said first free end (12) in order to apply said efforts on the elongate flexible element (5), and the second lever (15) comprises a second free end (16) which can be actuated by a movement of said second free end (16) in order to apply said efforts on the elongate flexible element (5).

16. The spiral spring according to any one of the preceding claims, characterised in that the first (8) and second (15) levers are configured to enable an adjustment of the effort(s) at different intensities.

17. The spiral spring according to claim 16, characterised in that the first (8) and second (15) levers have a section or a stiffness different from one another.

18. The spiral spring according to any one of the preceding claims, characterised in that the effort(s) is / are continuously adjustable by the prestressing means (6).

19. The spiral spring according to any one of the preceding claims, characterised in that the flexible element (5) and the levers (8, 15) are arranged at an outer end (4) of the strip (2).

20. A rotary resonator mechanism, in particular for a horological movement, including an oscillating mass, wherein it comprises a spiral spring (1) according to any one of the preceding claims.

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