Hairspring for watch resonator mechanism equipped with symmetrical stiffness adjustment means

Abstract

The invention relates to a hairspring, in particular for a watch resonator mechanism, the hairspring (100) comprising a flexible strip (2) wound on itself by multiple turns, the strip (2) having a predetermined stiffness, the hairspring (100) comprising means for adjusting the stiffness thereof, the means comprising a flexible element (5) arranged in series with the strip (2), a flexible element (5) connects one end (4) of the strip (2) to a fixed support (38) in order to add additional stiffness to a continuation portion of the strip (2), the flexible element (5) preferably having a greater stiffness than the strip (2), the flexible element (5) comprising two flexible portions (15, 16), each connecting the strip (2) to the fixed support (38), the two flexible portions (15, 16) being arranged so that the two flexible portions (15, 16) are connected to the fixed support (38). 16) are arranged in an axially symmetric manner with respect to each other along an axis (A), which preferably substantially passes through the center (O) of the hairspring. The invention also relates to a watch resonator mechanism comprising such a hairspring.

Description

Technical Field

[0001] The invention relates to a balance spring for a watch resonator mechanism, provided with a symmetrical device for adjusting the stiffness of said balance spring. The invention also relates to a watch resonator mechanism provided with such a balance spring. Background Art

[0002] In most mechanical watches, the energy required to rotate the hands (such as the minute and hour hands) is stored in a barrel and then transmitted by a balance-sprung system consisting of a flywheel called a balance combined with a spring in the form of a spirally wound strip called a hairspring.

[0003] The inner end of the balance spring is attached to the balance staff which rotates integrally with the balance wheel; the outer end of the balance spring is attached to a balance spring stud mounted on a stud holder which is itself integral with the fixed bridge (or balance cock).

[0004] The rotation of the balance wheel is maintained and its oscillations are counted by the escapement, which consists of a pallet fork performing a low-amplitude oscillating motion, provided with two pallets that engage with the teeth of the escape wheel. When the escape wheel is engaged in this way, it causes a step-by-step rotation of the escape wheel, the frequency of which is determined by the oscillation frequency of the pallet fork, which itself is set to the oscillation frequency of the balance-sprung system.

[0005] In a traditional escapement, the oscillation frequency is about 4 Hz, or about 28,800 vibrations per hour (V / h). One of the goals of a good watchmaker is to ensure the isochronism and regularity of the balance wheel's oscillations (or the constancy of its running time).

[0006] It is known to adjust the running error of a balance system with a hairspring by adjusting the effective length of the hairspring, which is defined as the length of the curve between the inner end of the hairspring and a counting point, which is located near the outer end of the hairspring and is usually defined by a pair of stops carried by a pin mounted on the regulator system.

[0007] In operation, the regulator index cannot rotate about the axis of the balance spring. However, its angular position can be fine-tuned manually, for example using a screwdriver to rotate an eccentric wheel on the regulator index that acts like a cam.

[0008] The assembly comprising the bridge, index system, pins, stud holder, hairspring stud, balance staff, hairspring and balance wheel is generally referred to as the "regulating mechanism". Examples of regulating mechanisms are given in International Application WO 2016 / 192957 and European Patent EP 2876504, both belonging to watch manufacturer ETA.

[0009] With some regulator systems, one end of the balance spring is attached to its stud holder, and the regulator pin has enough play to allow the balance spring to move between two stops. However, the amplitude-dependent chronometric characteristics, especially the anisochronism, are very sensitive to the play at the regulator pin, which is difficult to control accurately.

[0010] In some devices, these stops can be adjusted to tighten the balance spring in order to eliminate play, especially during its operation. In this case, the balance spring is first adjusted by moving the regulator pin, and then tightening the balance spring with the pin. However, tightening the balance spring with the regulator pin may stress the balance spring and produce timing errors, especially due to the winding being off-center. Moreover, eliminating play will also change the balance spring, and once the balance spring is tightened, it is no longer possible to move the regulator pin along the balance spring to achieve fine adjustment of the balance spring.

[0011] Other balance springs have integrated adjustment devices. In these balance springs, the travel time is adjusted not by varying the effective length of the balance spring, but by applying a force or torque to a flexible element arranged in series with the balance spring. In practice, the flexible element is placed in series with the strip, between one end of the strip and a fixed mount, in order to vary the stiffness of the connection point and provide additional flexibility to the resonator. The effective stiffness of the resonator thus includes the stiffness of the strip and the stiffness of the flexible element.

[0012] Thus, a variable force or torque is applied to prestress the flexible element. By prestressing the flexible element, its stiffness (from which the restoring force acting on the balance-sprung system is partly generated) varies, while the stiffness of the strip remains unchanged. By varying the stiffness of the flexible element, the stiffness of the entire resonator (stiffness of the strip and stiffness of the flexible element) varies, thus varying the travel time of the resonator and enabling precise adjustment of the frequency of the time base. This provides high precision in adjusting the travel time, since only one element is used to adjust the stiffness.

[0013] Such a balance spring equipped with an elastic element is described, for example, in patent application EP4009115 filed on behalf of Omega SA.

[0014] However, the geometry of the flexible element creates a risk of creeping of the adhesive used to attach the fixed support of the balance spring in the movement. In fact, the position of the fixed support and the orientation of the forces or torques applied to the flexible element can stress the adhesive, which can cause it to creep and thus alter the precision of regulation.

[0015] In addition, the direction in which the adjustment force is applied may be different from the intended direction due to manufacturing, assembly or alignment errors, etc. This difference will change the timing error and reduce the adjustment accuracy.

[0016] In addition, due to shocks and friction, the regulating mechanism may experience hysteresis, as the direction of the applied force changes and does not return to its original direction after the shock. This results in a change in the running error and a decrease in the regulation accuracy. Summary of the invention

[0017] The object of the present invention is to overcome some or all of the above-mentioned drawbacks, in particular to minimize the sensitivity to changes in the direction of the regulating force, by providing a balance spring equipped with an effective and precise regulating device, in particular configured to regulate the run of a timepiece by varying the effective stiffness of said balance spring.

[0018] To this end, the invention relates to a balance spring for a watch resonator mechanism, comprising a flexible strip wound a plurality of times on itself, the strip having a predetermined stiffness, the balance spring comprising adjustment means for adjusting its stiffness, the adjustment means comprising a flexible element arranged in series with the strip, the flexible element connecting one end of the strip to a fixed support so as to add additional stiffness to the continuation of the strip, the stiffness of the flexible element preferably being greater than that of the strip.

[0019] The invention is notable in that the flexible element comprises two flexible portions, each connecting the strip to a fixed support, the two portions being arranged in an axisymmetric manner relative to one another along an axis (A) which preferably passes substantially through the centre of the balance spring.

[0020] Thanks to the symmetrical arrangement of the flexible element in two parts, it is possible to apply a variable force or torque that is balanced, thus avoiding the risk of creeping of the adhesive used to attach the fixed support in the movement. In fact, the force or torque is more evenly distributed on the flexible element and therefore more evenly on the junction between the fixed support and the movement.

[0021] According to a particular embodiment of the invention, the flexible element is arranged at the outer end of the strip.

[0022] According to a particular embodiment of the invention, the two flexible portions are substantially identical.

[0023] According to a particular embodiment of the present invention, each flexible portion comprises one or two flexible necks.

[0024] According to a particular embodiment of the invention, each flexible portion comprises a translation table equipped with two substantially parallel flexible blades and a movable rigid portion connected to the strip.

[0025] According to a particular embodiment of the invention, the flexible element comprises a flexible guide provided with two offset blades.

[0026] According to a particular embodiment of the present invention, the flexible portion comprises a flexible blade.

[0027] According to a particular embodiment of the invention, each flexible portion comprises a flexible arm connected to the strip.

[0028] According to a particular embodiment of the present invention, each flexible portion comprises a flexible hook.

[0029] According to a particular embodiment of the invention, the adjustment means comprises prestressing means for applying a variable force or torque to the flexible element in order to change only the stiffness of the flexible element.

[0030] According to a particular embodiment of the invention, the prestressing device is configured to apply a variable force or torque to each portion of the flexible element.

[0031] According to a particular embodiment of the present invention, the torque or force can be continuously adjusted by means of a prestressing device.

[0032] According to a particular embodiment of the invention, the prestressing device is configured to apply the same variable force or torque to each portion of the flexible element.

[0033] According to a particular embodiment of the invention, the prestressing means comprises a screw configured to bear against the flexible element.

[0034] According to a specific embodiment of the present invention, the prestressing device comprises two flexible rods, each of which is connected to a flexible portion.

[0035] According to a particular embodiment of the invention, the prestressing means comprises two springs, each spring being connected to a flexible portion.

[0036] According to a particular embodiment of the invention, the prestressing means comprises a secondary flexible blade connected to each flexible portion.

[0037] According to a specific embodiment of the present invention, the two rods are connected to each other via a movable body.

[0038] The invention also relates to a rotating resonator mechanism, in particular for a watch movement, comprising an oscillating mass and such a balance spring. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The objects, advantages and features of the invention will become apparent from a number of embodiments given by way of non-limiting example only with reference to the accompanying drawings, in which:

[0040] - Figure 1 Schematically showing a top view of a balance spring according to a first embodiment of the present invention,

[0041] - Figure 2 Schematically showing a top view of a balance spring according to a second embodiment of the present invention,

[0042] - Figure 3 Schematically showing a top view of a balance spring according to a third embodiment of the present invention,

[0043] - Figure 4 Schematically showing a top view of a balance spring according to a fourth embodiment of the present invention,

[0044] - Figure 5 Schematically showing a top view of a balance spring according to a fifth embodiment of the present invention,

[0045] - Figure 6 Schematically showing a top view of a balance spring according to a sixth embodiment of the present invention,

[0046] - Figure 7 Schematically showing a top view of a balance spring according to a seventh embodiment of the present invention,

[0047] - Figure 8 Schematically showing a top view of a balance spring according to an eighth embodiment of the present invention,

[0048] - Fig. 9 Schematically showing a top view of a balance spring according to a ninth embodiment of the present invention,

[0049] - Fig.10 Schematically showing a top view of a balance spring according to a tenth embodiment of the present invention,

[0050] - Fig.11 Schematically showing a top view of a balance spring according to an eleventh embodiment of the present invention,

[0051] - Fig.12 Schematically showing a top view of a balance spring according to a twelfth embodiment of the present invention,

[0052] - Fig.13 schematically shows a top view of a balance spring according to a thirteenth embodiment of the present invention, and

[0053] - Fig.14 is based on Fig.13 A partial enlarged view of the hairspring of the thirteenth embodiment of the present invention. DETAILED DESCRIPTION

[0054] Figures 1 to 13Schematic diagrams of different embodiments of a balance spring 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, respectively, in particular for a watch resonator mechanism. In this case, the balance spring extends substantially in one plane. The balance spring 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110 comprises a flexible strip 2 wound a plurality of times on itself, the strip 2 having a predetermined stiffness. The balance spring has an adjustment device for adjusting its stiffness. The adjustment device can be actuated, for example, when the balance spring is mounted on a plate of a watch movement.

[0055] The adjustment device comprises a flexible element 5 arranged in series with the strip 2, the flexible element 5 connecting one end 4, 9 of said strip 2 to a fixed support 11, 14, 17, 24, 29, 38, 44 integral with one of the ends 4, 9 of the strip 2. The flexible element 5 adds additional rigidity to the strip 2. The rigidity of the flexible element 5 is preferably greater than the rigidity of the strip 2. The flexible element 5 is arranged as a continuation of the strip 2, in its extension. The adjustment device 5 and the strip 2 are preferably integral, or even made of the same material.

[0056] Balance spring 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120 also comprises prestressing means 6 for applying a variable force or torque to flexible element 5. In this way, the stiffness of balance spring 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110 can be adjusted, in particular in order to improve the accuracy of the movement's run-time error.

[0057] The ends of the strips 2 preferably remain substantially immobile, regardless of how the prestressing means are adjusted. Forces or torques applied to the flexible element 5 do not change the position of the ends 4 of the strips 2 to which the flexible element is connected. Only the flexible element 5 is acted upon to change its stiffness, and not directly on the strips 2. This provides greater precision, since only one element is used to adjust the stiffness. During oscillation, the ends 4 of the strips 2 may move.

[0058] In addition, the torque or force can be adjusted continuously by the prestressing device 6. In other words, the torque or force is not limited to discrete values / point values. Therefore, the stiffness of the flexible element 5 can be adjusted very accurately.

[0059] The prestressing means 6 preferably allow the flexible element 5 to translate or rotate in the plane of the balance spring. In this way, the stiffness of the flexible element 5 can be varied.

[0060] The embodiment described below comprises a flexible element 5 integral with the outer end 4 of the strip 2. The inner end 9 of the strip 2 is connected to the mounting / colt 3 of the oscillating mass of the resonator. In an alternative embodiment not shown in the figures, the flexible element is connected to the inner end of the strip, being arranged in series between the strip and the oscillating mass mounting.

[0061] exist Figures 1 to 13 In the described embodiments of balance springs 1 , 10 , 20 , 30 , 40 , 50 , 60 , 70 , 80 , 90 , 100 , 110 , 120 , flexible element 5 comprises two flexible portions 15 , 16 each connecting strip 2 to a fixed support 11 , 14 , 17 , 24 , 29 , 38 , 44 .

[0062] According to the invention, the two flexible portions 15 , 16 are arranged relative to one another in an axisymmetrical manner along the axis A of the balance spring. In other words, the two flexible portions 15 , 16 are positioned symmetrically about said axis A.

[0063] Axis A preferably passes substantially through the centre O of balance spring 1 , 10 , 20 , 30 , 40 , 50 , 60 , 70 , 80 , 90 , 100 , 110 , 120 , and axis A preferably passes through outer end 4 of strip 2 .

[0064] Therefore, the two flexible portions 15 , 16 are arranged on the periphery of the balance spring such that they are arranged at the same distance from the center O of the balance spring 1 , 10 , 20 , 30 , 40 , 50 , 60 , 70 , 80 , 90 , 100 , 110 , 120 .

[0065] The two flexible portions 15, 16 are preferably arranged with respect to each other with a "mirror" effect about the axis A. To this end, the two flexible portions 15, 16 are preferably substantially identical.

[0066] The prestressing means 6 preferably applies substantially the same force or torque to each flexible portion 15, 16. The directions of the forces are preferably substantially parallel.

[0067] In a variant, the prestressing means 6 apply to each flexible portion 15 , 16 a force or torque independent of each other.

[0068] Alternatively, the prestressing means 6 applies a single force or torque which is preferably redistributed in a substantially equal manner over the two flexible portions 15 , 16 .

[0069] In the balance spring 1 of the first embodiment, the regulating means comprise a single flexible blade 7 as flexible portion 15, 16. The flexible element 5 also comprises a forked fixed support 14 having two prongs 17, 18. Each flexible blade 7 connects the end 4 of the strip 2 to a different prong 17, 18 of the fixed support 14. In the rest position of the balance spring 1, the flexible blades 7 are arranged on the same axis.

[0070] exist Figure 2 In the example shown, each flexible portion 15, 16 of the flexible element 5 of the balance spring 1 comprises a neck 8 of reduced material thickness, which is flexible. The flexible element 5 also comprises a fork-shaped fixed support 14 with two prongs 17, 18, as in the first embodiment. Each neck 8 connects the end 4 of the strip 5 to the prongs 17, 18, respectively, and these necks 8 are arranged in the same direction.

[0071] Figure 3 The third embodiment of balance spring 10 shown has a flexible portion comprising two flexible necks connected by a rigid section.

[0072] exist Figure 4 In the fourth embodiment of the balance spring 20 shown, each flexible portion 15, 16 of the flexible element 5 of the balance spring 20 comprises a pivot with an offset flexible blade. In this case, the pivot comprises two offset flexible blades 51, 52 connected on the one hand to the end 4 of the strip 2 and, on the other hand, connected by moving away from each other to the tip of the fixed support 24. The first flexible blade of each pivot is arranged tangentially to the end 4, and the second flexible blade is inclined by moving away from the end 4.

[0073] Figure 5 , 6 7 show a balance spring 30, the flexible part of which the flexible element 5 comprises a translation stage. The translation stage comprises two flexible blades. The flexible blades 21, 22 are substantially parallel and arranged along different lines. The flexible blades 21, 22 of the translation stage are preferably connected to the same face 25 of the fixed support. The rigid part 23 has an elongated rectangular shape, to which the outer end 4 of the strip 2 is connected in its extension located on one side of the rigid part 23. The secondary flexible blades 21, 22 are substantially perpendicular to the rigid part 23 and the outer end 4. In the figure, the variable force or torque is preferably applied to the rigid part 23 parallel to the blades 21, 22.

[0074] exist Figure 5 In the embodiment, the fixed support 14 takes the form of a double-pronged fork, wherein the blades of the translation stage connect the end 4 to the prongs of said fork. These blades are arranged in a direction tangential to the end 4 of the strip 2.

[0075] exist Figure 6In the balance spring 50, the flexible blades of the translation stage of each flexible portion 16, 17 are substantially parallel to the symmetry axis A of the flexible element 5. Each fixed support 29 is in the form of an inverted T, and these flexible blades connect the top of the T to the end 4 of the strip 2. The end 4 has an elongated shape tangential to the strip 2, and the flexible blades of the translation stage are connected to the end 4.

[0076] To vary the overall stiffness of the balance springs 1,10,20,30,40,50 in the previous embodiments, the prestressing device 6 applies a variable force or torque to each flexible portion 16,17 of the flexible element 5. For example, the forces F1,F2 are represented by arrows pointing to the flexible portions 16,17.

[0077] This changes the stiffness of the flexible portions 15 , 16 of the flexible element 5 , and therefore the stiffness of the assembly comprising the strip 2 and the flexible element 5 .

[0078] The prestressing means 6 comprise, for example, a screw (not shown in the figures) which is in contact with each flexible portion 16 , 17 to apply said forces F1 , F2 .

[0079] Alternatively, the prestressing means 6 comprise one or more actuators in contact with the flexible portions 16 , 17 of the flexible element 5 .

[0080] The variable force or torque applied to each flexible portion 15, 16 is preferably the same. However, in these embodiments, the variable force or torque applied to each flexible portion 15, 16 may be different.

[0081] exist Figure 7 In the balance spring 60, the flexible blades of the translation stage for each flexible portion 16, 17 are substantially parallel to the axis of symmetry A of the flexible element 5. Each fixed support 29 is in the form of an inverted T, and these flexible blades connect the top of the T to the end 4 of the strip 2. The end 4 has an elongated shape tangential to the strip 2 and the flexible blades of the translation stage are connected to the end 4.

[0082] Figure 7 The flexible portion 16, 17 of the balance spring 60 in the embodiment of the present invention comprises two mobile bodies 35, 36, each of which is connected to the end 4 of the strip 2 by a secondary flexible blade 7 substantially tangential to the strip 2. The flexible blades 42, 43 of the translation stage connect the mobile bodies 35, 36 to the fixed support 29 in the form of an inverted T and are substantially perpendicular to the secondary flexible blade 7.

[0083] The prestressing device 6 also comprises a third mobile body 19 in the form of an arc of a circle, connected to the two mobile bodies 35, 36 of the flexible element 5 by means of two flexible rods 26, 27. Each flexible rod 26, 27 partially surrounds the winding strip 2. The third mobile body 19 is arranged on the other side of the balance spring 60 relative to the fixed support 38.

[0084] In order to vary the overall stiffness of balance spring 60, prestressing device 6 applies a variable force or torque to third mobile body 19 of prestressing device 6. Force F is represented by an arrow pointing to third mobile body 19, for example. Force F is preferably parallel to axis A.

[0085] In this case, substantially the same force is transmitted from a single force F applied to the third mobile body 19 via the two rods 26 , 27 to the two flexible portions 16 , 17 of the flexible element 5 .

[0086] exist Figure 8 In the embodiment shown in FIG. 1 , the flexible portions 15 , 16 of the flexible element 5 of the balance spring 70 have rounded flexible hooks 28 instead of the tips of the fixed supports 44 . The tips of the flexible hooks 28 point toward the end 4 of the strap 2 and are connected to the end 4 of the strap 2 by a single flexible blade 7 .

[0087] The flexible hook 28 is also connected by two flexible rods 26 , 27 to a body in the form of an arc of a circle, which is arranged on the other side of the balance spring 70 relative to the fixed support 29 , as in the previous embodiment.

[0088] Fig. 9 and 10 The embodiment of the hairspring 90 in the embodiment comprises flexible parts 15, 16, each of which is equipped with a translation stage 31, a single flexible blade 7 and a first moving body 32, and Figure 7 The same as in the embodiment.

[0089] The first moving body 32 is curved, and the blade 33 of the translation stage 31 is arranged at one end of the first moving body 32 .

[0090] The prestressing device 6 further comprises a spring 34 connecting the first moving body 32 to the second moving body 37. In this case, the spring 34 is formed by a plurality of substantially parallel tertiary blades (eg three tertiary blades) connected to the other end of the first moving body 32.

[0091] The second mobile body 37 is disposed on both sides of the hairspring 80. The second mobile body 37 receives a variable force or torque and transmits the force or torque to the first mobile body 32 via the spring 34.

[0092] exist Fig.10In an embodiment of the hairspring 90 , the prestressing device 6 further comprises two rods 39 , each of which connects the second mobile body 37 to a third mobile body 41 in the form of an arc, the third mobile body 41 being arranged on the other side of the hairspring 90 relative to the fixed support 38 .

[0093] The variable force or torque is applied to the third mobile body 41, for example by means of an actuator or a screw in contact with the third mobile body 41. The variable force or torque is at least partially transmitted to the flexible portions 15, 16 of the flexible element 5 via the spring 34.

[0094] Fig.11 The eleventh embodiment of the balance spring 100 in FIG. 1 shows flexible portions 15, 16 comprising two first mobile bodies 49 each connected by a neck 53 to a fixed support 38 in the form of an inverted T. Each first mobile body 49 is also connected by a single flexible blade 7 to the outer end 4 of the strip 2.

[0095] The prestressing device 6 also comprises two rods 26 each connecting a second mobile body 37 to a third mobile body 19 in the form of an arc of a circle, arranged on the other side of the balance spring 100 relative to the fixed support 38 .

[0096] The variable force or torque is applied to the third mobile body 19, for example by means of an actuator or a screw in contact with the third mobile body 19. The variable force or torque is at least partially transmitted via the rod 26 to the neck 53 of the flexible portion 15, 16 of the flexible element 5.

[0097] exist Fig.12 In the twelfth embodiment shown, the flexible portions 15, 16 each comprise a bent flexible rod 54, preferably formed in a semicircular shape, extending from the end of the fixed support 44 in the form of an inverted T. Each bent flexible rod 54 is also connected to the outer end 4 of the strip 2 by a single flexible blade 7.

[0098] The prestressing device 6 also comprises two rods 26 each connecting a curved flexible rod 54 to a mobile body 19 in the form of an arc of a circle, arranged on the other side of the balance spring 110 relative to the fixed support 44 .

[0099] The variable force or torque is applied to the third mobile body 19, for example by means of an actuator or a screw in contact with the third mobile body 19. The variable force or torque is at least partially transmitted via the rod 26 to each curved flexible rod 54 of the flexible portion 15, 16 of the flexible element 5.

[0100] Fig.13 The thirteenth embodiment shown in Fig.12. The bent rod is replaced by a curved flexible blade 55. The fixed support 53 takes the form of an open trapezoid, the long sides of which are open towards the outer end 4 of the strip 2. The mobile body 19 is U-shaped and, since it is arranged tangentially to the rod 26, it is able to engage with an actuator 57 equipped with a hook or finger inserted into the U.

[0101] Fig.14 yes Fig.13 1 . The curved blade 55 forms a semicircular curve, from which a single flexible blade 7 extends at one end and a fixed support 53 extends at the other end. The end 56 of the fixed support itself forms a curve with an inverse curvature opposite to that of the curved blade 55. The end 56 of the support 53 is semi-rigid and can therefore be partially deformed.

[0102] This arrangement of curvature and reverse curvature makes it possible to avoid changing the isochronism of the speed regulating mechanism when using the adjustment device to change the travel time difference. In fact, the force exerted on the top of the curved blade 55 is compensated by the reaction force of the reverse curvature of the end 56, such as Fig.14 As shown by the arrow in . Therefore, only a single flexible blade 7 is subjected to the force or torque applied by the prestressing device 6.

[0103] The flexible blade described in the various embodiments of the balance spring may be a continuous flexible blade, as is generally the case in the figures, or may be a blade having rigid sections and a flexible neck connecting these rigid sections.

[0104] The invention also relates to a rotating resonator mechanism, in particular for a watch movement. The resonator mechanism comprises an oscillating mass, not shown in the figures, and a hairspring as described above. The oscillating mass is, for example, an annular balance. The oscillating mass is combined with the hairspring and thus is integral with the support.

Claims

1. A balance spring (1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120), in particular for a watch resonator mechanism, comprising a flexible strip (2) wound a plurality of times on itself, said strip (2) having a predetermined stiffness, said balance spring comprising adjustment means for adjusting its stiffness, said adjustment means comprising a flexible element (5) arranged in series with said strip (2), said flexible element (5) connecting one end (4, 9) of said strip (2) to a fixed support (11, 14, 17, 24, 29, 38, 44, 53) in order to add additional stiffness to the continuation of said strip (2), said flexible element (5) preferably having a stiffness greater than that of said strip (2), characterised in that The flexible element (5) comprises two flexible portions (15, 16), each of which connects the strip (2) to the fixed support (11, 14, 17, 24, 29, 38, 44, 53), the two flexible portions (15, 16) being arranged relative to each other in an axisymmetrical manner along an axis (A) which preferably passes substantially through the center (O) of the balance spring.

2. The balance spring according to claim 1, characterized in that: The two flexible portions (15, 16) are substantially identical.

3. The balance spring according to claim 1 or 2, characterized in that: The flexible element (5) is arranged at the outer end (4) of the strip (2).

4. A balance spring according to any one of the preceding claims, characterised in that Each flexible portion (15, 16) comprises one or two flexible necks (8, 53).

5. The balance spring according to any one of claims 1 to 3, characterized in that Each flexible portion (15, 16) comprises a translation stage equipped with two substantially parallel flexible blades (21, 22, 42, 43, 74, 78) and a movable rigid portion (23, 45) connected to the strip (2).

6. A balance spring according to any one of claims 1 to 3, characterized in that Each flexible portion (15, 16) comprises a flexible guide provided with two offset blades (51, 52).

7. A balance spring according to any one of claims 1 to 3, characterized in that Each flexible portion (15, 16) comprises a flexible arm (18) connected to the strip (2).

8. A balance spring according to any one of claims 1 to 3, characterized in that Each flexible portion (15, 16) comprises a flexible blade (7).

9. A balance spring according to any one of claims 1 to 3, characterized in that Each flexible portion (15, 16) comprises a flexible hook portion (28).

10. A balance spring according to any one of the preceding claims, characterised in that The adjustment device comprises a prestressing device (6) for applying a variable force or torque to the flexible element (5) in order to change only the stiffness of the flexible element (5).

11. The balance spring according to claim 10, characterized in that: The prestressing device (6) is configured to apply a variable force or torque to each portion of the flexible element (5).

12. A balance spring according to any one of the preceding claims, characterised in that: The force or torque can be continuously adjusted by means of the prestressing device (6).

13. A balance spring according to any one of the preceding claims, characterised in that The prestressing device (6) is configured to apply the same variable force or torque to each portion of the flexible element (5).

14. A balance spring according to any one of the preceding claims, characterised in that The prestressing device (6) comprises a screw configured to bear against the flexible element (5).

15. A balance spring according to any one of claims 1 to 13, characterized in that The prestressing device (6) comprises two flexible rods (26), each of which is connected to a flexible part (15, 16).

16. The balance spring according to claim 15, characterized in that The prestressing device (6) comprises two springs (34), each spring (34) being connected to a flexible portion (15, 16).

17. A balance spring according to any one of claims 1 to 13, characterized in that The prestressing device (6) comprises a secondary flexible blade (7) connected to each flexible portion (15, 16).

18. A balance spring according to any one of claims 15 to 17, characterized in that The two flexible rods (26) are connected to each other via a moving body (19, 41).

19. A rotating resonator mechanism, in particular for a watch movement, comprising an oscillating mass, characterized in that The rotary resonator mechanism comprises a balance spring (1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120) according to any one of the preceding claims.

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