Hairspring for a timepiece regulating member provided with temperature-dependent adjustment means

Abstract

The invention relates to a spiral spring, in particular for a timepiece regulating organ, the spiral spring (100) comprising a flexible ribbon (2) wound on itself in several turns, the ribbon (2) having a predefined stiffness, the spiral spring (100) comprising means for adjusting its stiffness, the spiral spring (1) comprising actuating means (10) for actuating the adjustment means, characterized in that the actuating means (10) actuate the adjustment means as a function of the ambient temperature. The invention also relates to a timepiece regulating organ comprising such a spiral spring.

Description

Technical field of the invention

[0001] The invention relates to a hairspring for a timepiece regulating organ, the hairspring being provided with temperature-dependent adjustment means. The invention also relates to a timepiece regulating organ provided with such a hairspring. Technological background

[0002] In most mechanical watches, the energy required to rotate the hands (e.g., the minute and hour hands) is stored in a barrel and then delivered by a balance-spring system, which includes a flywheel called a balance wheel, combined with a spring in the form of a spiral-wound ribbon called a balance spring.

[0003] At one internal end, the balance spring is fixed to a shaft which rotates with the balance wheel; at one external end, the balance spring is fixed to a stud mounted on a stud holder which is itself fixed to a fixed bridge (or balance cock).

[0004] The rotation of the balance wheel is maintained - and its oscillations counted - by an escapement mechanism comprising an anchor driven by a low-amplitude oscillating movement, equipped with two pallets which engage the teeth of an escape wheel. Thus engaged, the escape wheel is imposed a step-by-step rotational movement whose frequency is determined by the oscillation frequency of the anchor, itself set to the oscillation frequency of the balance spring).

[0005] In a traditional escapement mechanism, the oscillation frequency is about 4 Hz, or about 28,800 vibrations per hour (A / h). One of the goals of good watchmakers is to ensure isochronism and regularity of the oscillations (or constancy of the rate) of the balance wheel.

[0006] It is known to regulate the rate of the balance wheel by adjusting the active length of the balance spring, defined as the curvilinear length between its internal end and a counting point, located near the external end of the balance spring and generally defined by a pair of stops carried by a key mounted on a rack system.

[0007] In operation, this index system is fixed in rotation relative to the balance spring axis. However, it is possible, by manual intervention, to finely adjust its angular position, e.g. by pivoting, using a screwdriver, an eccentric acting on the index system in the manner of a cam.

[0008] The assembly comprising the bridge, the index system, the key, the stud holder, the stud, the arbor, the spring and the balance wheel is commonly referred to as a "regulating organ". Examples of regulating organs are provided by international application WO 2016 / 192957 and by European patent EP 2 876 504, both in the name of the watch manufacturer ETA.

[0009] There are indexing systems that have a stud holder to which one end of the hairspring is attached, and whose indexing system key leaves a clearance to allow the hairspring to move between the two stops. However, the chronometric properties, in particular the anisochronism as a function of the amplitude, are very sensitive to the play in the index key, while this play is difficult to control precisely.

[0010] In some devices, the stops are adjustable to tighten the hairspring to eliminate play, especially during operation of the hairspring. In this case, the rate is first adjusted by moving the index key, then the hairspring is tightened with the key. But tightening the hairspring with the index key risks constraining it, and creating timekeeping defects, particularly by off-centering of the coils. In addition, removing play also modifies the rate, and once the hairspring is tightened, the index key can no longer be moved along the hairspring to finish fine-tuning the rate.

[0011] Other hairsprings have a built-in adjustment device. In these hairsprings, the rate is not adjusted by changing the effective length of the hairspring, but by applying a force or torque to an elastic element arranged in series with the hairspring. In effect, a flexible element is placed in series with the ribbon between one end of the ribbon and a fixed support to change the stiffness of the attachment point and provide additional flexibility to the resonator. Thus, the effective stiffness of the resonator includes the stiffness of the ribbon and the stiffness of the flexible element.

[0012] A variable force or torque is then applied to pre-stress the flexible element. By pre-stressing the flexible element, its stiffness, which partly results in the restoring force acting on the balance, changes, while the stiffness of the ribbon remains unchanged. By changing this stiffness of the flexible element, the stiffness of the entire resonator (stiffness of the ribbon and stiffness of the flexible element) changes, which consequently changes the rate of the resonator, and allows the frequency of the time base to be precisely adjusted. This achieves great precision in the adjustment of the rate, because only one element is used to adjust the stiffness.

[0013] Such a spiral spring equipped with an elastic element is for example described in patent application EP4009115 filed in the name of Omega SA.

[0014] However, ambient temperature has a significant impact on the rate of a regulating organ comprising such a balance spring and a flywheel. Indeed, the balance wheel and / or the balance spring expands or contracts depending on the ambient temperature. These variations in dimensions cause deviations in the rate of the regulating organ.

[0015] In addition, the elastic constants also change depending on the ambient temperature and modify the stiffness of the hairspring.

[0016] To reduce these differences, regulating organs have been developed, configured to compensate for the effect of temperature. For example, by using a bimetallic balance, or in the case of balance springs made of silicon, a layer of silicon oxide is added, which has a thermoelastic coefficient inverse to that of the silicon from which the balance spring is formed (see patent EP1422436).

[0017] However, these configurations are only effective around a specific predefined temperature, and they are no longer effective enough, when the temperature moves away from this specific temperature. Summary of the invention

[0018] The aim of the present invention is to overcome all or part of the drawbacks mentioned above, in particular to minimize the sensitivity of the regulating member to changes in ambient temperature, by proposing a spiral spring provided with effective adjustment means which adapt to the ambient temperature, even when the temperature variations are significant.

[0019] To this end, the invention relates to a spiral spring for a timepiece regulating organ, the spiral spring comprising a flexible ribbon wound on itself in several turns, the ribbon having a predefined stiffness, the spiral spring comprising means for adjusting its stiffness, the spiral spring comprising actuating means for actuating the adjustment means.

[0020] The invention is remarkable in that the actuating means actuate the adjustment means as a function of the ambient temperature.

[0021] By means of the actuating means, variations in the dimensions of the balance spring and / or the balance wheel, and thermoelastic variations of the balance spring due to temperature are compensated, in particular to compensate for the quadratic effect of the temperature on the rate of the regulating organ. Thus, variations in the rate of the regulating organ comprising said balance spring and an inertia flywheel are avoided, due to the temperature variation.

[0022] According to a particular embodiment of the invention, the actuating means comprise an element deformable as a function of temperature.

[0023] According to a particular embodiment of the invention, the deformable element comprises a temperature-sensitive material.

[0024] According to a particular embodiment of the invention, the deformable element is a bimetallic strip.

[0025] According to a particular embodiment of the invention, the deformable element comprises a microstructure, or even a nanostructure.

[0026] According to a particular embodiment of the invention, the actuating means comprise a support body which is movable thanks to the deformable element, which moves it according to its deformation according to a plurality of positions.

[0027] According to a particular embodiment of the invention, the adjustment means comprising a flexible element arranged in series with the ribbon, the flexible element connecting one end of said ribbon to a fixed support, so as to add additional stiffness to the continuation of the ribbon, the flexible element preferably having a stiffness greater than that of the ribbon.

[0028] According to a particular embodiment of the invention, the adjustment means comprise prestressing means for applying a variable force or torque to the flexible element, so as to vary the stiffness of the flexible element.

[0029] According to a particular embodiment of the invention, the support body is in contact with the prestressing means.

[0030] According to a particular embodiment of the invention, the support body comprises a rod provided with a first end mounted on the deformable element, and a second end mounted on the prestressing means.

[0031] According to a particular embodiment of the invention, the actuating means comprise a fixed pin, which allows the rod to form a lever.

[0032] According to a particular embodiment of the invention, the flexible element comprises two flexible parts each connecting the ribbon to the fixed support, the two flexible parts being arranged relative to each other by axial symmetry along an axis, the axis preferably passing substantially through the center of the spiral spring.

[0033] According to a particular embodiment of the invention, the prestressing means comprise two flexible levers each connected to a flexible part.

[0034] According to a particular embodiment of the invention, the two levers are connected to each other by a movable body.

[0035] The invention also relates to a regulating organ, in particular for a watch movement, comprising an oscillating mass and such a balance spring. Brief description of the figures

[0036] The aims, advantages and characteristics of the present invention will appear on reading several embodiments given solely as non-limiting examples, with reference to the appended drawings in which: there Figure 1 schematically represents a top view of a spiral spring according to a first embodiment of the invention, the spiral spring being in a first configuration, the Figure 2 schematically represents a top view of the spiral spring of the Figure 1 in a second configuration, the Figure 3 schematically represents a top view of the spiral spring of the Figure 1 in a third configuration, the Figure 4 represents a graph showing the effect of the adjustment means on the temperature variation, the Figure 5 schematically represents a top view of a spiral spring according to a second embodiment of the invention, and the Figure 6schematically represents a top view of a spiral spring according to a third embodiment of the invention. Detailed description of the invention

[0037] THE figures 1 to 3 each show a schematic representation of a first embodiment of a hairspring 1, in particular for a timepiece regulating organ. The three figures show three different configurations of the hairspring 1.

[0038] Here, the spiral spring 1 extends substantially in a plane. The spiral spring 1 comprises a flexible ribbon 2 wound on itself in several turns, the ribbon 2 having a predefined stiffness.

[0039] The hairspring includes means for adjusting its stiffness. For example, the adjustment means are particularly operable when the hairspring is mounted in a regulating organ, in particular assembled on a plate of a watch movement.

[0040] The adjustment means comprise a flexible element 5 arranged in series with the ribbon 2, the flexible element 5 connecting an outer end 4 of said ribbon 2 to a fixed support 53 and secured to the outer end 4 of the ribbon 2. The flexible element 5 adds additional stiffness to that of the ribbon 2. The flexible element 5 preferably has a stiffness greater than that of the ribbon 2. The flexible element 5 is arranged after the ribbon 2, in its extension. Preferably, the adjustment means 5 and the ribbon 2 are in one piece, or even formed from the same material. The hairspring 1 further comprises prestressing means 6 for applying a variable force or torque to the flexible element 5. Thus, the stiffness of the hairspring 1 can be adjusted, in particular to improve the accuracy of the movement's operation.

[0041] In this embodiment of the spiral spring, the flexible element 5 comprises two flexible parts 15, 16 each connecting the ribbon 2 to a fixed support 53.

[0042] The two flexible parts 15, 16 are arranged, one with respect to the other, by axial symmetry along an axis A of the spiral spring 1. In other words, the two flexible parts 15, 16 are positioned so as to be symmetrical with respect to said axis A.

[0043] On the one hand, the axis A passes substantially through the center O of the spiral spring, and on the other hand, the axis A passes, preferably, through the external end 4 of the ribbon 2.

[0044] Thus, the two flexible parts 15, 16 are arranged at the periphery of the spiral spring, so that the two flexible parts 15, 16 are arranged at the same distance from the center 0 of the spiral spring 1.

[0045] The two flexible parts 15, 16 are preferably arranged relative to each other in a "mirror" type position relative to the axis A. For this purpose, the two flexible parts 15, 16 are preferably substantially identical.

[0046] The flexible parts 15, 16 each comprise a curved flexible blade 55, preferably forming a semicircle, and extending from the end of the fixed support 53. Each curved flexible blade 55 is further connected to the external end 4 of the ribbon 2 by a main flexible blade 7. The main flexible blades 7 are here arranged in the extension of one another.

[0047] The curved blade 55 forms a semi-circular rounding, which is extended by the single flexible blade 7 at one end and by the fixed support 53 on the other hand. The end 56 of the support itself forms a rounding with a counter-curvature opposite that of the curved blade 55. The end 56 of the support 53 is semi-rigid so that it can partially deform.

[0048] This arrangement of curvature and counter-curvature makes it possible to avoid modifying the isochronism of the regulating member, when the rate is modified with the adjustment means. In fact, the force which is exerted on the top of the curved blade 55, is compensated by the reaction force of the counter-curvature of the end 56, as represented by the arrows in Figure 14. Thus, only the single flexible blade 7 undergoes the force or torque applied by the prestressing means 6.

[0049] The fixed support 53 has the shape of a trapezoid open on the large side towards the external end 4 of the ribbon 2.

[0050] The adjustment means of the spiral spring 1 further comprise pre-stressing means 6 for applying a variable force or torque to the flexible element 5. Thus, the stiffness of the spiral spring 1 can be adjusted. The torque or force is continuously adjustable by the pre-stressing means 6. In other words, the torque or force is not restricted to point values. Thus, the stiffness of the flexible element 5 can be adjusted with great precision.

[0051] Preferably, the prestressing means 6 apply a substantially identical force or torque to each flexible part 15, 16, from a single force F applied to the third body 19, via the two levers 14, 26. The directions of the forces are preferably substantially symmetrical with respect to the axis A.

[0052] The prestressing means 6 further comprise two levers 14, 26 each connecting a curved blade 55 to the same movable body 19, preferably rigid, arranged on the other side of the spiral spring 1 relative to the fixed support 53. The movable body 19 here has the shape of an arc of a circle.

[0053] The variable force or torque is applied to the movable body 19. The variable force or torque is at least partly transmitted to the main flexible blades 7 of the flexible parts 15, 16 of the flexible element 5, via the levers 14, 26.

[0054] Preferably, the torque or force is continuously adjustable by the prestressing means 6. In other words, the torque or force is not restricted to point values. Thus, the stiffness of the flexible element 5 can be adjusted with great precision.

[0055] The spiral spring 1 further comprises actuating means 10 for actuating the pre-stressing means 6.

[0056] According to the invention, the actuating means 10 actuate the prestressing means 6 as a function of the ambient temperature. Thus, the actuating means 10 make it possible to compensate for the effect of the temperature variation on the regulating member, by acting on the spiral spring 1, by modifying the stiffness in order to maintain a constant rate of the regulating member.

[0057] To this end, the actuating means 10 comprise a deformable element 11 depending on the temperature. The deformable element 11 has the advantages of deforming depending on the temperature in a controlled manner.

[0058] In an alternative embodiment, the deformable element 11 comprises, for example, a deformable liquid or semi-liquid element, which is for example used in a thermometer, such as mercury or alcohol. This liquid or semi-liquid element is contained in an enclosure provided with a movable wall, which moves according to the deformation of the liquid or semi-liquid element as a function of the temperature.

[0059] Alternatively, the deformable element 11 is a metal that is very sensitive to temperature.

[0060] The actuating means 10 further comprise a support body 12 in contact with the prestressing means 6, here the movable body 19. The support body 12 is also in contact with the deformable element 11. Thus, the support body 12 is movable thanks to the deformable element.

[0061] For example, in the case of a liquid or a semi-liquid as a deformable element, the support body 12 is in contact with the movable wall, which moves the support body 12 according to the deformation of the deformable element 11.

[0062] In the case of a metal material, the support body 12 is in direct contact with it.

[0063] In the figures, the support body 12 comprises a rod 13 forming a lever against the prestressing means 6. The rod 13 comprises two ends 17, 18, a first end 17 being mounted on the deformable element 11, and a second end 18 being mounted against the prestressing means 6.

[0064] The actuating means 10 further comprise a pin 21, intended to be fixed relative to the rest of the regulating member, and against which the rod 13 can be brought into contact. The pin 21 has a fulcrum function to enable the rod to form a lever. The pin 21 also forms a reference point for the operation of the regulating member.

[0065] The pin 21 is for example arranged in a position corresponding substantially to the middle of the rod 13. Thus, when the rod 13 is in contact with the pin 21, it bears on the pin 21 to transmit a force provided by the deformation of the deformable element 11.

[0066] Preferably, the pin 21 comprises a section, which is not circular, for adjusting the actuation of the deformable element 11.

[0067] On the Figure 1, the rod 13 is in contact with the movable body 19 of the prestressing means 6, and it rests against the pin 21. The rod 13 exerts a force on the movable body 19 to obtain a predetermined stiffness of the spiral spring 1. For example, a predetermined stiffness is chosen for an ambient temperature of 20 degrees.

[0068] In a variant, the pin 21 is offset relative to the center of the rod 13, in order to have a greater lever arm, when actuating the rod 13.

[0069] In the configuration of the Figure 2 , the deformable element 11 has expanded due to a higher temperature. The deformable element 11 pushes back the rod 13, which is no longer in contact with the pin 21. The force exerted on the movable body 19 is increased, so that the stiffness of the flexible element 5 is modified.

[0070] Thus, the effect of the increase in temperature on the regulating organ is compensated by the increase in the force exerted on the prestressing means 6.

[0071] In the configuration of the Figure 3 , the ambient temperature has decreased, so that the deformable element has contracted. Thus, not only is the rod 13 brought back against the pin 21, but in addition, it pushes the movable body 19 back by leverage. In fact, the rod presses on the pin 21, so that the second end pushes the movable body 19 away from the prestressing means 6.

[0072] Therefore, the stiffness of the flexible element 5 is modified to compensate for the effect of the drop in ambient temperature on the regulating member.

[0073] In both cases, whether it is a drop or an increase in the ambient temperature, the actuating means 10 push the movable body 19 to modify the stiffness of the flexible element 5.

[0074] On the Figure 4 , the graph shows three superimposed curves 22, 23, 24 describing the effect of temperature on the operation of a regulating organ.

[0075] The lower curve 24 describes the variation of the rate as a function of temperature, when there is no compensation according to the invention. Thus, when the temperature increases or decreases, the difference in rate compared to the rate at 23°C decreases. Such a curve can be produced with spiral springs mentioned in patent EP1605182.

[0076] The upper curve 22 describes the variation of the step, which is obtained by the actuation means 10 according to the invention.

[0077] The middle curve 23 represents the effect obtained on the operation of the regulating member thanks to the actuating means 10 according to the invention when the ambient temperature varies. The operation remains substantially constant, even if the temperature varies greatly.

[0078] Indeed, thanks to the actuation means 10, the effect of the actuation means 10, represented on the upper curve 22, compensates for the effect of the temperature variation represented on the lower curve 24, so that the step remains substantially constant despite the temperature difference.

[0079] A second embodiment of spiral spring 1 is shown in the Figure 5 , in which the spiral spring 1 is substantially identical to the first embodiment, except for the deformable element 27 of the adjustment means 10. Here, the deformable element 27 comprises a bimetallic strip, or bimetallic strip, which deforms depending on the temperature.

[0080] The bimetallic strip is curved, and comprises a first end 29 assembled to a fixed support 31 outside the spiral spring 1. A second end 28 of the bimetallic strip is associated with the first end 17 of the rod 12. The second end 28 of the bimetallic strip is in contact with the first end 17 of the rod 12.

[0081] When the ambient temperature changes, the bimetallic strip bends more or less. Thus, the second end 28 of the bimetallic strip pulls or pushes the first end 17 of the rod 12, which actuates the prestressing means 6.

[0082] Therefore, depending on the curvature of the bimetallic strip, the rod 13 is moved, similarly to the first embodiment.

[0083] Such a bimetallic strip is well known to those skilled in the art.

[0084] In the third embodiment of the Figure 6, the deformable element 28 comprises a microstructure, or even a nanostructure, for example alveolar, which deforms depending on the temperature. Such a microstructure, or even a nanostructure, is configured to deform, in a manner similar to the first embodiment.

[0085] Thus, depending on the deformation of the microstructure, or even a nanostructure, the rod 13 is moved in a manner similar to the first embodiment.

[0086] 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.

[0087] The invention also relates to a regulating member, not shown in the figures, in particular for a watch movement. The regulating member comprises, for example, an oscillating weight and a balance spring as described above. The oscillating weight is for example an annular balance. The oscillating weight is joined to the balance spring to be secured to the support.

Claims

1. Spiral spring, in particular for a timepiece regulating organ, the spiral spring (1) comprising a flexible ribbon (2) wound on itself in several turns, the ribbon (2) having a predefined stiffness, the spiral spring (1) comprising means for adjusting its stiffness, the spiral spring (1) comprising actuating means (10) for actuating the adjustment means, characterized in that the actuating means (10) actuate the adjustment means according to the ambient temperature.

2. Spiral spring according to claim 1, characterized in that the actuating means (10) comprise a deformable element (11) depending on the temperature.

3. Spiral spring according to claim 2, characterized in that the deformable element (11) comprises a temperature-sensitive material.

4. Spiral spring according to claim 2 or 3, characterized in that the deformable element (11) comprises a bimetallic strip.

5. Spiral spring according to claim 2 or 3, characterized in that the deformable element (11) comprises a microstructure, or a nanostructure.

6. Spiral spring according to any one of claims 2 to 5, characterized in that the actuating means (10) comprise a support body (12) movable thanks to the deformable element (11), which moves it according to its deformation according to a plurality of positions.

7. Spiral spring according to any one of claims 2 to 6, characterized in that the adjustment means comprising a flexible element (5) arranged in series with the ribbon (2), the flexible element (5) connecting one end (4, 9) of said ribbon (2) to a fixed support (53), so as to add additional stiffness following the ribbon (2), the flexible element (5) preferably having a stiffness greater than that of the ribbon (2).

8. Spiral spring according to claim 7, characterized in thatthe adjustment means comprising prestressing means (6) for applying a variable force or torque to the flexible element (5), so as to vary the stiffness of the flexible element (5), 9. Spiral spring according to claim 8, characterized in that the support body (12) is in contact with the prestressing means (6).

10. Spiral spring according to claim 9, characterized in that the support body (11) comprises a rod (13) provided with a first end (17) mounted on the deformable element (12), and a second end (18) mounted on the prestressing means (6).

11. Spiral spring according to claim 9 or 10, characterized in that the actuating means (10) comprise a fixed pin (21), which allows the rod (13) to form a lever.

12. Spiral spring according to any one of claims 7 to 11, characterized in thatthe flexible element (5) comprises two flexible parts (15, 16) each connecting the ribbon (2) to the fixed support (53), the two flexible parts (15, 16) being arranged relative to each other by axial symmetry along an axis (A), the axis (A) preferably passing substantially through the center (0) of the spiral spring.

13. Spiral spring according to claim 11 or 12, characterized in that the prestressing means (6) comprise two flexible levers (14, 26) each connected to a flexible part (15, 16).

14. Spiral spring according to claim 13, characterized in that the two levers (14, 26) are connected to each other by a movable body (19).

15. Regulating organ, in particular for a watch movement, comprising an oscillating weight, characterized in that it comprises a spiral spring (1) according to any one of the preceding claims.

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