Spiral spring for resonator mechanism of a clock with means for adjusting stiffness

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 rate adjustment, there are adjustment mechanisms consisting of one or more screws arranged in the balance wheel's rim. By adjusting the screws, the balance wheel's inertia 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 2 781 970 A1 shows an active length adjustment mechanism for a watch balance spring. 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 operation 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.

[0011] The invention is remarkable in that the adjustment means comprise a first elongated flexible element, and a second elongated flexible element, each arranged in series with the ribbon, each elongated flexible element connecting one end of said ribbon to a fixed support, so as to add additional stiffness to the ribbon, each elongated flexible element preferably having a stiffness greater than that of the ribbon, the adjustment means comprising prestressing means for applying at least two different adjustable forces, the two forces being applied to the first elongated flexible element so as to vary the stiffness of the first elongated flexible element according to the level of prestress.

[0012] Thanks to the invention, the stiffness of at least one of two elongated flexible elements, such as flexible blades, can be modified. Indeed, when two forces such as those mentioned previously are applied, 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. By applying two perpendicular forces to a blade, longitudinally and orthogonally, a combined force is obtained, which changes the stiffness of the elongated flexible element. The combination of two forces is essential to achieve this.

[0013] By adjusting the prestressing elements, the intensity of the stress is modulated, resulting in a change in the stiffness of the assembly comprising the elongated flexible elements and the ribbon. Indeed, the flexible elements connected in series with the ribbon provide additional stiffness, which combines with that of the ribbon. Thus, when the prestressing elements apply varying forces to at least one of the elongated flexible elements, they modify the stiffness of that flexible element and therefore of the assembly comprising the ribbon and the flexible elements, 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, and it also provides additional flexibility to the resonator. Thus, 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 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 rate, allowing for precise adjustment of our timebase frequency. This results in highly accurate rate tuning, as we are only subtly adjusting the stiffness of the spiral spring by modifying a single additional element.

[0016] According to a particular embodiment of the invention, the first effort is provided by a first tensile / compressive force directed substantially in the longitudinal direction. FL of the first elongated flexible element.

[0017] According to a particular embodiment of the invention, the first effort also exerts a first force directed substantially in a substantially orthogonal direction. FT to the longitudinal direction of the second elongated flexible element.

[0018] According to a particular embodiment of the invention, the second effort is provided by a second force directed substantially in a substantially orthogonal direction. FT to the longitudinal direction of the first elongated flexible element.

[0019] According to a particular embodiment of the invention, the second effort also exerts a second tensile / compressive force directed substantially in the longitudinal direction. FL of the second elongated flexible element.

[0020] According to a particular embodiment of the invention, the first and second elongated flexible elements each comprise a unique flexible blade.

[0021] According to a particular embodiment of the invention, the first and second elongated flexible elements each comprise a pair of main flexible blades.

[0022] According to a particular embodiment of the invention, the first flexible element is arranged in a radial direction of the spiral spring.

[0023] According to a particular embodiment of the invention, the second flexible element is arranged in a direction tangential to the spiral spring.

[0024] According to a particular embodiment of the invention, the first and second elongated flexible elements are substantially perpendicular to each other.

[0025] According to a particular embodiment of the invention, the prestressing means comprise two secondary flexible blades connected at the end, each secondary flexible blade being arranged in the extension of one of the elongated flexible elements.

[0026] According to a particular embodiment of the invention, the prestressing means comprise two rigid bodies arranged each at the end of each secondary flexible blade.

[0027] According to a particular embodiment of the invention, the prestressing means comprise variable support means on each rigid body.

[0028] According to a particular embodiment of the invention, the forces are continuously adjustable by means of prestressing.

[0029] According to a particular embodiment of the invention, the first and second flexible elements are arranged at an external end of the ribbon.

[0030] According to a particular embodiment of the invention, the end of the ribbon comprises an appendage, the prestressing means and the elongated flexible elements being joined to the appendage.

[0031] According to a particular embodiment of the invention, the end of the ribbon is more rigid than the elongated flexible elements and the ribbon.

[0032] According to a particular embodiment of the invention, the elongated flexible elements comprise a flexible neck.

[0033] According to a particular embodiment of the invention, the prestressing means are configured to allow adjustment of the two forces to different intensities.

[0034] 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 :

[0035] 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 a first embodiment of the invention, and the figure 2schematically represents a top view of a spiral spring according to a second embodiment of the invention. Detailed description of the invention

[0036] THE figures 1 and 2 Each figure shows a schematic representation of a different embodiment of a balance spring 1, 10, particularly for a resonator mechanism in a watch. Here, the balance spring extends substantially in the same plane. The balance spring 1, 10 comprises a flexible ribbon 2 wound around itself in several turns, the ribbon 2 having a predefined stiffness. The balance spring 1, 10 includes means for adjusting its stiffness. For example, the adjustment means can be operated when the balance spring 1, 10 is mounted on a plate of a watch movement, not shown in the figures.

[0037] According to the invention, the adjustment means comprise a first 5 and a second elongated flexible element 15 extending longitudinally. Each flexible element 5, 15 is arranged in series with the ribbon 2, the first 5 and the second flexible element 15 connecting a single end 4 of said ribbon 2 to a fixed support 11, 14. In other words, the ribbon 2 is connected to the fixed support 11, 14 solely by these two flexible elements 5, 15.

[0038] The flexible elements 5, 15 are attached to one end 4 of the ribbon 2. Preferably, the two flexible elements 5, 15 are arranged perpendicularly to each other.

[0039] The embodiments described below include flexible elements 5, 15 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.

[0040] The flexible elements 5, 15 add additional stiffness to that of the ribbon 2. The flexible elements 5, 15 preferably have a stiffness greater than that of the ribbon 2. The first flexible element 5 is arranged here in line with the ribbon 2, while the second flexible element 15 is arranged perpendicular to the first flexible element 5. Preferably, the adjustment means and the ribbon 2 are one piece, or even made of the same material.

[0041] Furthermore, the outer end 4 of the ribbon 2 is bent perpendicularly to form an appendage 9. The appendage 9 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 elements 5, 15, to minimize its influence on the stiffness of the ribbon 2.

[0042] In the first embodiment, each elongated flexible element 5, 15 is a single flexible blade 13, 15 connecting the appendage 9 to the fixed support 11. The first single flexible blade 13 is arranged in line with the appendage 9, while the second single flexible blade 13 is arranged in a direction substantially perpendicular to the appendage 9.

[0043] Thus, the first single 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, while the second flexible blade is arranged in a tangential direction to the ribbon 2.

[0044] In the second embodiment of the figure 2, each elongated flexible element 5, 15 comprises a pair of main blades 23, 25 extending from the appendage 9 to the fixed support 11. The main blades 23, 25 of each pair spread apart from the appendage 9 to the fixed support 11 and form, for example, an angle between 10 and 40° between them.

[0045] The spiral spring 1 further includes preload means 6 for applying at least two different forces to at least one of the flexible elements 5, 15, preferably both flexible elements 5, 15. For example, the two forces are applied to the first flexible element 5,

[0046] Both efforts are preferably longitudinal forces. FL of tension-compression, and an orthogonal force FT, which are variable. The longitudinal force FL is directed along the longitudinal direction of the first flexible element 5, while the orthogonal force FT,is directed along a direction perpendicular to the longitudinal direction of the first flexible element 5, the two forces preferably belonging to the plane of the spiral spring 1, 10. Thus, the stiffness of the first flexible element 5 can be modified, and the action of the spiral spring 1, 10 can be adjusted, in particular to improve the accuracy of the movement's action.

[0047] We act on the first flexible element 5 to modify its stiffness without acting directly on the ribbon 2. However, during oscillations, the end 4 of the ribbon 2 can be mobile.

[0048] Furthermore, the longitudinal forces FL and orthogonal FT are continuously adjustable by means of prestressing 6. In other words, the forces FL And FT are not restricted to discrete values. Thus, the stiffness of the flexible element 5 can be finely adjusted with high precision.

[0049] In addition, the prestressing means 6 are configured to modify the stiffness of the second flexible element 15.

[0050] Indeed, the first effort also exerts a first force directed substantially in a direction substantially orthogonal to the longitudinal direction of the second elongated flexible element 15. As the two flexible elements 5, 15 are arranged perpendicularly to each other, a longitudinal force applied on one of the elongated flexible elements 5, 15 generates a substantially orthogonal force applied on the other flexible element.

[0051] Similarly, the second effort also exerts a second tensile / compressive force directed substantially in the longitudinal direction of the second elongated flexible element 15.

[0052] To apply these adjustable forces, the prestressing means 6 include two means for applying a force to the elongated flexible elements 5, 15.

[0053] The application means each include two secondary flexible blades 12, 13. Each secondary flexible blade 12, 13 is arranged in the extension of the elongated flexible element 5, 15, and is fixed on the other side of the appendage 9.

[0054] The two secondary flexible blades 12, 13 are arranged perpendicularly to each other.

[0055] Alternatively, the secondary blades 12, 13, can be replaced by standard springs.

[0056] Each secondary flexible blade 12, 13 has a rigid body 14, 16 at its free end. The rigid body 14, 16 allows a variable force to be applied to the secondary flexible blade 12, 13 in order to adjust the force transmitted to the elongated flexible element 5, 15.

[0057] By moving the rigid bodies 14, 16, a longitudinal force is applied. FL variable and an orthogonal force FT variable on appendix 9, according to each direction of movement of each rigid body 19, 21. Thus, the stiffness of the elongated flexible elements 5, 15 is modified. By moving the rigid bodies 19, 21, the value of the force exerted on the single flexible blade 15 is modified.

[0058] The prestressing means 6 further include variable support means on the rigid body 14, 16. By actuating the support means, the rigid body 14, 16 moves, so that the secondary flexible blade 12, 13 is more or less flexed, and consequently transmits a greater or lesser force on the elongated flexible element 5, 15. Thus, the rigidity of the elongated flexible element 5, 15 is modified, so that the path of the spiral spring is modified, and can be adjusted.

[0059] The variable support means are for example a screw 24 in contact with the rigid body 14, 16, and arranged longitudinally according to the direction of the secondary flexible blade 12, 13. Thus, by moving the screw 24, the secondary flexible blades 12, 13 exert a greater or lesser force on the appendage 9, and therefore on the elongated flexible elements 5, 15.

[0060] Alternatively, variable support means include a spring fixed at one end to the rigid body, and a movable body arranged at the other end of the spring. Thus, by moving the movable body, the spring exerts a greater or lesser force on the secondary flexible blade.

[0061] In another variant, the prestressing means include a first magnet mounted on the rigid body, and a second, movable magnet positioned at a distance from the rigid body. Thus, by changing the distance of the second magnet relative to the first magnet, the force applied to the secondary flexible blade is modified.

[0062] Alternatively, a pivoting lever can be used, assembled to the rigid body at one end, the other end being free and serving as a means of actuating the lever by moving said free end.

[0063] Preferably, the prestressing means are configured to allow adjustment of both forces, here the two longitudinal tensile / compressive forces at different intensities. Thus, a first application means allows adjustment within a wider adjustment range, and a second application means allows adjustment within a finer adjustment range.

[0064] To this end, the secondary flexible blades 12, 13 may, for example, have different cross-sections or lengths. Alternatively, the variable support means on the rigid bodies 14, 16 are configured to obtain different adjustment ranges, for example with a different screw pitch.

[0065] The invention also relates to a clockwork mechanism comprising such a balance spring. The balance spring is notably used to power the movement of a balance wheel.

[0066] 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.

[0067] 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.

[0068] Furthermore, the flexible blades can be oriented in directions other than radial and orthogonal to the spiral spring. Thus, they can be oriented in any direction between radial and orthogonal.

Claims

1. A spiral spring, in particular for a horological resonator mechanism, the spiral spring (1, 10) comprising a flexible strip (2) coiled on itself into several turns, the strip (2) having a predefined stiffness, the spiral spring (1, 10) including means for adjusting its stiffness, the adjustment means including a first elongate flexible element (5), and a second elongate flexible element (15) arranged in series with the strip (2), each elongate flexible element (5, 15) connecting the same end (4, 9) of said strip (2) to a fixed support (11, 14), so as to add an additional stiffness to the strip (2), each elongate flexible element (5) preferably having a stiffness higher than that of the strip (2), the adjustment means including prestressing means (6) for applying at least two different adjustable efforts, the two efforts being applied on the first elongate flexible element (5) so as to make the stiffness of the first elongate flexible element (5) vary according to the prestress level.

2. The spiral spring according to claim 1, characterised in that the first effort is imparted by a first tensile / compressive force directed substantially in the longitudinal direction FL of the first elongate flexible element (5).

3. The spiral spring according to claim 1, characterised in that the first effort further exerts a first force directed substantially in a direction substantially orthogonal to the longitudinal direction of the second elongate flexible element (15).

4. The spiral spring according to any one of the preceding claims, characterised in that the second effort is imparted by a second force directed substantially in a direction substantially orthogonal FT to the longitudinal direction of the first elongate flexible element (5).

5. The spiral spring according to claim 4, characterised in that the second effort further exerts a second tensile / compressive force directed substantially in the longitudinal direction of the second elongate flexible element (15).

6. The spiral spring according to any one of the preceding claims, characterised in that each of the first (5) and second (15) elongate flexible elements includes a unique flexible blade (13, 18).

7. The spiral spring according to any one of claims 1 to 5, characterised in that each of the first (5) and second (15) elongate flexible elements includes a pair of main flexible blades (23, 25).

8. The spiral spring according to any one of the preceding claims, characterised in that the first (5) and second (15) elongate flexible elements are substantially perpendicular to one another.

9. The spiral spring according to any one of the preceding claims, characterised in that the first flexible element (5) is arranged in a radial direction of the spiral spring (1, 10).

10. The spiral spring according to any one of the preceding claims, characterised in that the second flexible element (15) is arranged in a direction tangential to the spiral spring (1, 10).

11. The spiral spring according to any one of the preceding claims, characterised in that the prestressing means (6) comprise two secondary flexible blades (12, 13) connected at the end (4), each secondary flexible blade (12, 13) being arranged in line with one of the elongate flexible elements (5, 15).

12. The spiral spring according to claim 11, characterised in that the prestressing means (6) include two rigid bodies (14, 16) each arranged at the end of each secondary flexible blade (12, 13).

13. The spiral spring according to claim 12, characterised in that the prestressing means (6) include variable support means on each rigid body (14, 16).

14. The spiral spring according to any one of the preceding claims, characterised in that the efforts are continuously adjustable by the prestressing means (6).

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

16. The spiral spring according to any one of the preceding claims, characterised in that the prestressing means (6) are configured to enable an adjustment of the two efforts at different intensities.

17. A rotary resonator mechanism, in particular for a horological movement, including an oscillating mass, wherein it comprises a spiral spring (1, 10) according to any one of the preceding claims.