Balance-spring for timepiece resonator mechanism comprising symmetrical rigidity adjustment means, and timepiece resonator mechanism

Abstract

To provide a balance-spring comprising effective and accurate adjustment means.SOLUTION: Provided is a balance-spring 100 for a timepiece resonator mechanism in particular. The balance-spring 100 comprises a flexible strip 2 wound around the balance-spring itself using multiple coils. The strip 2 has prescribed rigidity, and the balance-spring 100 includes means for adjusting the rigidity of the strip. The adjustment means includes a flexible element 5 aligned in series with the strip 2. In the flexible element 5, an end 4 of the strip 2 is connected to a fixed mount 38 so as to impart additive rigidity to a connection part of the strip 2. The flexible element 5 preferably has rigidity that is larger than the rigidity of the strip 2. The flexible element 5 includes two flexible portions 15, 16. The two flexible portions 15, 16 respectively connects the strip 2 to the fixed mount 38. The two flexible portions 15, 16 are arranged in axial symmetry relative to each other along an axis A. Preferably, the axis A substantially passes through a center 0 of the balance-spring.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] The present invention relates to a hairspring for a timepiece resonator mechanism, the hairspring being provided with symmetry means for adjusting the stiffness of said hairspring. The present invention also relates to a timepiece resonator mechanism equipped with such a hairspring. [Background technology]

[0002] In the majority of mechanical watches, the energy required to rotate the hands (e.g. minute and hour hands) is stored in a barrel and then transferred by a spring balance system, known as a spring balance, which includes a flywheel combined with a spring in the form of a spirally wound strip known as a balance spring.

[0003] The inner end of the balance spring is attached to an integral shaft that rotates with the spring balance, and the outer end of the balance spring is attached to a balance spring stud mounted in a stud holder that is itself integral to a fixed bridge (or cock).

[0004] The escapement keeps the spring balance rotating and counts its oscillations. The escapement includes a pallet driven by a low-amplitude oscillating movement. The low-amplitude oscillating movement comprises two pallets which engage with the teeth of the escape wheel. When the escape wheel is thus engaged, it imposes a step-by-step rotational movement, the frequency of which is determined by the frequency of oscillation of the pallets. The pallets are themselves matched to the frequency of oscillation of the spring balance.

[0005] In a traditional escapement mechanism, the frequency of oscillation is approximately 4 Hz, or approximately 28,800 oscillations per hour (A / h). One of the aims of a good watchmaker is to ensure the isochronism and regular oscillation (or constant rate) of the spring balance.

[0006] It is a known practice to regulate the speed of a spring balance by adjusting the effective length of the balance spring, which is defined as the curved length between the inner end of the balance spring and a count point located near the outer end of the balance spring, typically defined by a pair of stops supported by pins mounted on an index assembly system.

[0007] In operation, the indexing assembly system is rotatably fixed relative to the axis of the balance spring, however, its angular position can be manually fine-tuned, for example, by using a screwdriver to rotate a cam-like acting eccentric in the indexing assembly system.

[0008] The assembly including the bridge, index assembly system, pin, stud holder, balance spring stud, shaft, balance spring and spring balance is commonly known as a "regulator". Examples of regulators are described in US Pat. Nos. 5,399,413 and 5,443,633, both in the name of the watch manufacturer ETA.

[0009] There are index assembly systems that have a stud holder to which one end of the balance spring is attached, where the pin of the index assembly system leaves enough play to allow the balance spring to move between two stops. However, the chronometric characteristics, especially the anisochronism as a function of amplitude, are very sensitive to the play in the index pin, and it is difficult to control this play precisely.

[0010] In certain devices, the stop can be adjusted to tighten the hairspring, in particular to eliminate play during the operation of the hairspring. In this case, the speed is adjusted first by moving the index pin and then by tightening the hairspring with the pin. However, tightening the hairspring with the index pin puts stress on the hairspring, especially with the risk of the coil becoming eccentric and causing chronometer failure. In addition, the elimination of play also alters the speed, since once the hairspring is tightened, it is no longer possible to move the index pin along the hairspring to complete the fine adjustment of the speed.

[0011] Other hairsprings have an integral adjustment device. In these hairsprings, the speed is adjusted not by modifying the effective length of the hairspring, but by applying a force or torque to a flexible element arranged in series with the hairspring. In effect, placing a flexible element in series with the strip between one end of the strip and a fixed mount modifies the stiffness of the pinning point, giving the resonator more flexibility. Thus, the effective stiffness of the resonator includes the stiffness of the strip and the stiffness of the flexible element.

[0012] A variable force or torque is then applied to prestress the flexible element. Prestressing the flexible element changes its stiffness, which in part creates the return force acting on the spring balance, while the stiffness of the strip remains unchanged. By modifying the stiffness of this flexible element, the stiffness of the entire resonator (stiffness of the strip and the stiffness of the flexible element) changes, so that the speed of the resonator is modified and the frequency of the time base can be precisely adjusted. This allows a high degree of precision when adjusting the speed, since only one element is used to adjust the stiffness.

[0013] A hairspring fitted with such an elastic element is described, for example, in patent application DE 10 200 03 133 A1 filed on behalf of the company Omega.

[0014] However, the geometric configuration of the flexible element poses a risk of creep affecting the adhesive used to attach the fixed mount for the balance spring in the movement: in effect, depending on the position of the fixed mount and the orientation of the force or torque applied to the flexible element, stresses are generated in the adhesive which lead to creep and therefore modify the precision of the adjustment.

[0015] In addition, the direction in which the adjustment force is applied may differ from the intended direction due to manufacturing errors, assembly errors, alignment errors, etc. This difference has the effect of modifying the speed, thereby reducing the accuracy of the adjustment.

[0016] In addition, due to shock and friction, there may be hysteresis in the adjustment mechanism as the direction of the applied force changes and does not return to the original direction after a shock, resulting in speed changes and poor adjustment accuracy. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] International Publication No. 2016 / 192957 [Patent Document 2] European Patent Application Publication No. 2876504 [Patent Document 3] European Patent Application Publication No. 4009115 Summary of the Invention

[0018] 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 adjusting force, in particular by providing a hairspring with effective and precise adjusting means adapted to adjust the speed of the timepiece by modifying the effective stiffness of said hairspring.

[0019] To this end, the invention relates to a hairspring for a timepiece resonator mechanism, comprising a flexible strip wound on itself with a number of coils, the strip having a given stiffness, the hairspring comprising means for adjusting said stiffness, the adjusting means comprising a flexible element arranged in series with the strip, the flexible element adding additional stiffness to the continuation of the strip by connecting one end of said strip to a fixed mount, the flexible element preferably having a stiffness greater than that of the strip.

[0020] The present invention is noted in that the flexible element comprises two flexible parts, each connecting a strip to a fixed mount, the two parts being arranged axially symmetrical to one another along an axis (A), the axis (A) preferably passing substantially through the centre of the balance spring.

[0021] Thanks to the symmetrical arrangement of the two parts of the flexible element, a balanced variable force or torque can be applied, avoiding the risk of creep affecting the adhesive used to attach the fixed mount to the movement: in effect, the force or torque is evenly distributed over the flexible element and therefore over the joint between the fixed mount and the movement.

[0022] According to a particular embodiment of the invention, the flexible elements are arranged at the outer ends of the strip.

[0023] According to a particular embodiment of the invention, the two flexible portions are substantially identical.

[0024] According to a particular embodiment of the invention, each flexible portion comprises one or two flexible necks.

[0025] According to a particular embodiment of the invention, each flexible portion comprises a translation table with two substantially parallel flexible blades and a movable rigid portion to which the strips are connected.

[0026] According to a particular embodiment of the invention, the flexible element comprises a flexible guide with two offset blades.

[0027] According to a particular embodiment of the present invention, the flexible portion comprises a flexible blade.

[0028] According to a particular embodiment of the invention, each flexible portion includes a flexible arm to which a strip is connected.

[0029] According to a particular embodiment of the invention, each flexible portion includes a flexible hook.

[0030] 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 so as to vary the stiffness of the flexible element only.

[0031] According to a particular embodiment of the invention, the prestressing means is configured to apply a variable force or torque to each portion of the flexible element.

[0032] According to a particular embodiment of the invention, the torque or force is continuously adjustable by means of prestressing means.

[0033] According to a particular embodiment of the invention, the prestressing means is configured to apply a variable force or torque to each portion of the flexible element.

[0034] According to a particular embodiment of the invention, the prestressing means comprises a screw arranged to abut against the flexible element.

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

[0036] According to a particular embodiment of the invention, the prestressing means comprises two springs, each spring connected to one flexible portion.

[0037] According to a particular embodiment of the invention, the prestressing means comprises a secondary flexible blade connected to each flexible portion.

[0038] According to a particular embodiment of the invention, the two levers are connected to each other by a movable body.

[0039] The invention also relates to a rotary resonator mechanism, in particular for a timepiece movement, including an oscillating weight and such a balance spring. [Brief description of the drawings]

[0040] The objects, advantages and features of the present invention will become apparent from a certain number of embodiments, given by way of non-exhaustive example only, with reference to the accompanying drawings, in which:

[0041] [Figure 1] FIG. 2 is a schematic top view of a hairspring according to a first embodiment of the present invention; [Diagram 2] FIG. 4 shows a schematic top view of a hairspring according to a second embodiment of the present invention. [Diagram 3] FIG. 13 shows a schematic top view of a hairspring according to a third embodiment of the present invention; [Figure 4] FIG. 13 shows a schematic top view of a hairspring according to a fourth embodiment of the present invention. [Diagram 5] FIG. 13 shows a schematic top view of a hairspring according to a fifth embodiment of the present invention; [Figure 6] FIG. 13 shows a schematic top view of a hairspring according to a sixth embodiment of the present invention. [Figure 7] FIG. 13 shows a schematic top view of a hairspring according to a seventh embodiment of the present invention. [Figure 8] FIG. 13 shows a schematic top view of a hairspring according to an eighth embodiment of the present invention; [Figure 9] FIG. 13 shows a schematic top view of a hairspring according to a ninth embodiment of the present invention. [Figure 10] FIG. 23 is a schematic top view of a hairspring according to a tenth embodiment of the present invention; [Figure 11]FIG. 16 shows a schematic top view of a hairspring according to an eleventh embodiment of the present invention. [Figure 12] FIG. 23 shows a schematic top view of a hairspring according to a twelfth embodiment of the present invention; [Figure 13] FIG. 23 shows a schematic top view of a hairspring according to a thirteenth embodiment of the present invention; [Figure 14] FIG. 14 is an enlarged view of a portion of the hairspring according to the thirteenth embodiment of the present invention shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] 1 to 13 respectively show schematic representations of different embodiments of a hairspring 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, in particular for a timepiece resonator mechanism. In this case, the hairspring extends substantially in one plane. The hairspring 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110 comprises a flexible strip 2 wound on itself with a number of coils, the strip 2 having a given stiffness. The hairspring comprises means for adjusting its stiffness. For example, the adjustment means can be activated when the hairspring is mounted on a plate of the timepiece movement.

[0043] The adjustment means comprises a flexible element 5 arranged in series with the strip 2, which connects one end 4, 9 of said strip 2 to a fixed mount 11, 14, 17, 24, 29, 38, 44 integral with one of the ends 4, 9 of the strip 2. The flexible element 5 adds an additional stiffness to that of the strip 2. The flexible element 5 preferably has a stiffness greater than that of the strip 2. The flexible element 5 is arranged in a continuation of the strip 2 in its extension. The adjustment means 5 and the strip 2 are preferably integral or made of the same material.

[0044] The balance spring 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120 also comprises prestressing means 6 which apply a variable force or torque to the flexible element 5. In this way, the stiffness of the balance spring 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110 can be adjusted in order to improve in particular the speed accuracy of the movement.

[0045] Preferably, the end of the strip 2 remains substantially immobile, regardless of the adjustment of the prestressing means. A force or torque applied to the flexible element 5 does not modify the position of the end 4 of the strip 2 to which it is connected. Only the flexible element 5 is acted upon to modify its stiffness, without the strip 2 being acted upon directly. This further improves the accuracy, since only one element is used to adjust the stiffness. During vibration, the end 4 of the strip 2 can become mobile.

[0046] In addition, the torque or force is continuously adjustable by the prestressing means 6. In other words, the torque or force is not limited to a one-off value. Thus, the stiffness of the flexible element 5 can be adjusted very precisely.

[0047] The prestressing means 6 preferably allow the flexible element 5 to move translationally or rotationally in the plane of the balance spring, in this way the stiffness of the flexible element 5 can be varied.

[0048] The embodiment described below includes a flexible element 5 integrated into the outer end 4 of the strip 2. The inner end 9 of the strip 2 is connected to a mount 3 of the seismic mass of the resonator. In an alternative embodiment not shown in the drawings, the flexible element is connected to the inner end of the strip such that it is in series between the strip and the seismic mass mount.

[0049] In the embodiments of the balance springs 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120 described in Figures 1 to 13, the flexible element 5 comprises two flexible parts 15, 16 connecting the strip 2 to the fixed mounts 11, 14, 17, 24, 29, 38, 44.

[0050] According to the invention, the two flexible parts 15, 16 are arranged axisymmetrically with respect to one another along the balance spring axis A. In other words, the two flexible parts 15, 16 are positioned symmetrically with respect to said axis A.

[0051] Preferably, the axis A passes substantially through the center 0 of the balance spring 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, and further preferably, the axis A passes through the outer end 4 of the strip 2.

[0052] That is, the two flexible portions 15, 16 are arranged on the outer periphery of the balance spring so as to be arranged at the same distance from the center 0 of the balance spring 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120.

[0053] The two flexible portions 15, 16 are preferably arranged relative to one another with a "mirror" effect relative to the axis A. To this end, the two flexible portions 15, 16 are preferably substantially identical.

[0054] The prestressing means 6 preferably exerts substantially the same force or torque on each flexible portion 15, 16. The directions of the forces are preferably substantially parallel.

[0055] In one variant, the prestressing means 6 exerts a force or torque on each flexible portion 15, 16 independent of each other.

[0056] Alternatively, the prestressing means 6 applies a single force or torque which is redistributed, preferably substantially evenly, across the two flexible portions 15,16.

[0057] In the first embodiment of the hairspring 1, the adjustment means comprises a single flexible blade 7 as the flexible portion 15, 16. The flexible element 5 also comprises a fork-shaped fixed mount 14 having two elongated extremities 17, 18. Each flexible blade 7 connects an end 4 of the strip 2 to a different elongated extremity 17, 18 of the fixed mount 14. The flexible blades 7 are arranged coaxially in the rest position of the hairspring 1.

[0058] In the example visible in figure 2, the flexible parts 15, 16 of the flexible element 5 of the hairspring 1 each include a neck 8 that is thinned in terms of material thickness, the necks 8 being flexible. The flexible element 5 also includes, as in the first embodiment, a fork-shaped fixed mount 14 having two elongated extremities 17, 18. Each neck 8 connects an end 4 of the strip 5 to an elongated extremity 17, 18, these necks 8 being arranged in the same direction.

[0059] The third embodiment of the hairspring 10 visible in FIG. 3 has a flexible portion including two flexible necks connected by a rigid section.

[0060] In a fourth embodiment of the hairspring 20 visible in figure 4, each flexible portion 15, 16 of the flexible element 5 of the hairspring 20 comprises a pivot with offset flexible blades. In this case, the pivot comprises two offset flexible blades 51, 52 connected by being pulled away from each other to the end 4 of the strip 2 on the one hand and to a projection of the fixed mount 24 on the other hand. The first flexible blade of each pivot is arranged tangentially to the end 4, while the second flexible blade is oblique by moving away from the end 4.

[0061] 5, 6 and 7 show a hairspring 30, the flexible part of which of the flexible elements 5 comprises a translation table. The translation table comprises two flexible blades 21, 22 which are substantially parallel and arranged on different lines. The flexible blades 21, 22 of the translation table are preferably attached to the same face 25 of the fixed mount. The rigid part 23 has an elongated rectangular shape, to one side of which the outer end 4 of the strip 2 is attached in its extension. The secondary flexible blades 21, 22 are substantially perpendicular to the rigid part 23 and to the outer end 4. In the figures, a variable force or torque is applied to the rigid part 23, preferably parallel to the blades 21, 22.

[0062] In Figure 5, the fixed mount 14 takes the form of a fork with two elongated ends, with the blades of the translation table connecting its end 4 to one elongated end of the fork, the blades being arranged tangentially towards the end 4 of the strip 2.

[0063] In the hairspring 50 of Figure 6, the flexible blade of the translation table of each flexible portion 16, 17 is substantially parallel to the axis of symmetry A of the flexible element 5. Each fixed mount 29 has the form of an inverted T, the flexible blade connecting the apex of the T to an end 4 of the strip 2. The end 4 has an elongated form in the tangential direction towards the strip 2, to which the flexible blade of the translation table is joined.

[0064] The prestressing means 6 applies a variable force or torque to each of the flexible portions 16, 17 of the flexible element 5 in order to modify the overall stiffness of the balance springs 1, 10, 20, 30, 40, 50 in the above embodiments. For example, a force F 1 , F 2 is represented by an arrow pointing towards the flexible parts 16,17.

[0065] This modifies 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 .

[0066] The prestressing means 6 may, for example, 1 , F 2 1 includes a screw (not shown in the drawings) that contacts each flexible portion 16, 17 to provide additional tension.

[0067] Alternatively, the prestressing means 6 comprises one or more actuators in contact with the flexible portions 16 , 17 of the flexible element 5 .

[0068] 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.

[0069] In the hairspring 60 of Figure 7, the flexible blade of the translation table of each flexible portion 16, 17 is substantially parallel to the axis of symmetry A of the flexible element 5. Each fixed mount 29 has an inverted T-shape, the flexible blade connecting the apex of the T to an end 4 of the strip 2. The end 4 has an elongated form in the tangential direction towards the strip 2, to which the flexible blade of the translation table is joined.

[0070] The flexible portion 16, 17 of the hairspring 60 in FIG. 7 comprises two mobile bodies 35, 36 each connected to an end 4 of the strip 2 by a secondary flexible blade 7 that is substantially tangential to the strip 2. Flexible blades 42, 43 of the translation table connect the mobile bodies 35, 36 to a fixed mount 29 in the form of an inverted T and are substantially perpendicular to the secondary blade 7.

[0071] The prestressing means 6 also includes a third mobile body 19 in the form of a circular arc. The third mobile body 19 is connected to two mobile bodies 35, 36 of the flexible element 5 via two flexible levers 26, 27. Each flexible lever 26, 27 partially surrounds the wound strip 2. The third mobile body 19 is arranged on the other side of the balance spring 60 relative to a fixed mount 38.

[0072] To modify the overall stiffness of the hairspring 60, the prestressing means 6 applies a variable force or torque to the third movable body 19 of the prestressing means 6. For example, a force F is represented by an arrow pointing towards the third movable body 19. The force F is preferably parallel to the axis A.

[0073] In this case, substantially the same force is transmitted from a single force F applied to the third mobile body 19 via the two levers 26 , 27 to the two flexible parts 16 , 17 of the flexible element 5 .

[0074] In figure 8 the flexible parts 15, 16 of the flexible element 5 of the hairspring 70 have a rounded flexible hook 28 instead of the elongated tip of the fixed mount 44. The tip of the flexible hook 28 is directed towards the end 4 of the strip 2 and is connected to the end 4 of the strip 2 by a single flexible blade 7.

[0075] The flexible hook 28 is also connected by two flexible levers 26, 27 to a body in the form of a circular arc arranged on the other side of the balance spring 70 relative to the fixed mount 29, as in the previous embodiment.

[0076] The embodiment of the hairspring 90 in FIGS. 9 and 10, like the embodiment in FIG. 7, comprises flexible parts 15, 16 each equipped with a translation table 31, a single flexible blade 7 and a first movable body 32.

[0077] The first movable body 32 is curved, and a blade 33 of the translation table 31 is arranged at one end of the first movable body 32 .

[0078] The prestressing means 6 also comprises a spring 34 connecting the first mobile body 32 to the second mobile body 37. In this case, the spring 34 is formed by a plurality of substantially parallel tertiary blades, for example three tertiary blades, connected to the other end of the first mobile body 32.

[0079] The second mover 37 is arranged on either side of the balance spring 80. The second mover 37 receives a variable force or torque and transmits it to the first mover 32 via the spring 34.

[0080] In the embodiment of the hairspring 90 of FIG. 10, the prestressing means 6 also include two levers 39 each connecting the second mobile body 37 to a third mobile body 41 in the form of a circular arc arranged on the other side of the hairspring 90 relative to a fixed mount 38.

[0081] A variable force or torque is applied to the third movable body 41, for example by an actuator or by a screw in contact with the third movable 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.

[0082] The eleventh embodiment of the hairspring 100 in FIG. 11 shows flexible parts 15, 16 including two first mobile bodies 49 each connected by a neck 53 to a fixed mount 38 in the form of an inverted T.

[0083] The prestressing means 6 also include two levers 26 each connecting a second mobile body 37 to a third mobile body 19 in the form of a circular arc arranged on the other side of the balance spring 100 relative to a fixed mount 38 .

[0084] A variable force or torque is applied to the third movable body 19, for example by an actuator or by a screw in contact with the third movable body 19. The variable force or torque is at least partially transmitted via the lever 26 to the neck 53 of the flexible parts 15, 16 of the flexible element 5.

[0085] In a twelfth embodiment, seen in Figure 12, the flexible portions 15, 16 each include a curved flexible rod 54. The curved flexible rods 54 preferably form a semicircle and extend from the end of the fixed mount 44 in the form of an inverted T. The curved flexible rods 54 are also each connected to the outer end 4 of the strip 2 by a single flexible blade 7.

[0086] The prestressing means 6 also include two levers 26 each connecting a curved flexible rod 54 to a mobile body 19 in the form of a circular arc arranged on the other side of the balance spring 110 relative to the fixed mount 44.

[0087] A variable force or torque is applied to the third movable body 19, for example by an actuator or by a screw in contact with the third movable body 19. The variable force or torque is at least partially transmitted via the lever 26 to each curved flexible rod 54 of the flexible parts 15, 16 of the flexible element 5.

[0088] The thirteenth embodiment, visible in figure 13, is a variant of the embodiment visible in figure 12. The curved rod is replaced by a curved flexible blade 55. The fixed mount 53 takes the form of a trapezoid with its long side open towards the outer end 4 of the strip 2. The mobile body 19 is U-shaped and arranged tangentially towards the lever 26 so that it can engage with an actuator 57 equipped with a hook or finger inserted into the U.

[0089] Figure 14 is an enlarged view of the curved blade 55 of the hairspring 120 in Figure 13. The curved blade 55 forms a semicircular curve, extended at one end by the single flexible blade 7 and at the other end by a fixed mount 53. The end 56 of the mount itself forms a curve with a reverse curvature opposite to that of the curved blade 55. The end 56 of the mount 53 is semi-rigid so as to be partially deformable.

[0090] This arrangement of curvature and reverse curvature makes it possible not to modify the isochronism of the adjustment member when the speed is modified using the adjustment means. In effect, the force acting on the apex of the curved blade 55 is compensated by the reaction force of the reverse curvature of the end 56, as shown by the multiple arrows in Figure 14. Thus, only a single flexible blade 7 is subjected to the force or torque applied by the prestressing means 6.

[0091] The flexible blades described in the various embodiments of the hairspring may be continuous flexible blades, as is generally the case in the drawings, or may be blades having rigid sections and flexible necks connecting the sections.

[0092] The invention also relates to a rotary resonator mechanism, in particular for a timepiece movement, which comprises an oscillating weight, not shown in the drawings, and a balance spring as described above, the oscillating weight being, for example, an annular spring balance, the oscillating weight being joined to the balance spring so as to be integral with the mount.

Claims

1. A hairspring, in particular for a timepiece resonator mechanism, comprising: said hairspring (1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120) comprising a flexible strip (2) wound on itself with a number of coils, said strip (2) having a given stiffness, said hairspring (1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120) comprising means for adjusting its stiffness, said adjusting means comprising a flexible element (5) arranged in series with said strip (2), said flexible element (5) connecting an end (4, 9) of said strip (2) to a fixed mount (11, 14, 17, 24, 29, 38, 44, 53) so as 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); A hairspring characterized in that said flexible element (5) comprises two flexible parts (15, 16), each of which connects said strip (2) to said fixed mount (11, 14, 17, 24, 29, 38, 44, 53), said two flexible parts (15, 16) being arranged axially symmetrically with respect to one another along an axis (A), said axis (A) preferably passing substantially through the center (0) of the hairspring.

2. 2. A balance spring according to claim 1, characterized in that the two flexible parts (15, 16) are substantially identical.

3. 2. A hairspring according to claim 1, characterized in that the flexible element (5) is arranged at the outer end (4) of the strip (2).

4. 2. A balance spring according to claim 1, characterized in that each flexible portion (15, 16) comprises one or two flexible necks (8, 53).

5. 2. A hairspring according to claim 1, characterized in that each flexible part (15, 16) comprises a translation table with two substantially parallel flexible blades (21, 22, 42, 43, 74, 78) and a movable rigid part (23, 45) to which said strip (2) is connected.

6. 2. A hairspring according to claim 1, characterized in that each flexible section (15, 16) comprises a flexible guide with two offset blades (51, 52).

7. 2. A balance spring according to claim 1, characterized in that each flexible portion (15, 16) comprises a flexible arm (18) to which said strip (2) is connected.

8. 2. A balance spring according to claim 1, characterized in that each flexible portion (15, 16) comprises a flexible blade (7).

9. 2. A hairspring according to claim 1, characterized in that each flexible portion (15, 16) comprises a flexible hook (28).

10. 2. A hairspring according to claim 1, characterized in that the adjusting means comprise prestressing means (6) for applying a variable force or torque to the flexible element (5) so as to vary the stiffness of only the flexible element (5).

11. 11. A hairspring according to claim 10, characterized in that the prestressing means (6) are arranged to apply a variable force or torque to each portion of the flexible element (5).

12. 2. The balance spring according to claim 1, characterized in that the torque or force is continuously adjustable by means of the prestressing means (6).

13. 2. A hairspring according to claim 1, characterized in that the prestressing means (6) are arranged to apply identical, variable forces or torques to each portion of the flexible element (5).

14. 2. A hairspring according to claim 1, characterized in that the prestressing means (6) comprise a screw arranged to abut against the flexible element (5).

15. 2. A balance spring according to claim 1, characterized in that the prestressing means (6) comprise two flexible levers (26) each connected to one of the flexible portions (15, 16).

16. 16. A balance spring according to claim 15, characterized in that the prestressing means (6) comprise two springs (34), each connected to a flexible portion (15, 16).

17. 2. A balance spring according to claim 1, characterized in that the prestressing means (6) comprise a secondary flexible blade (7) connected to each flexible portion (15, 16).

18. 16. The balance spring according to claim 15, characterized in that the two levers (26) are connected to each other via a movable body (19, 41).

19. A rotary resonator mechanism, in particular for a timepiece movement, comprising an oscillating weight, characterized in that it comprises a balance spring (1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120) according to claim 1.

Images