Device for the autonomous adjustment of the active length of a hairspring

Abstract

The present invention relates to a device (6) for autonomous adjustment of the active length of a balance spring (5), for a balance-spring type oscillator (4, 5), comprising a cock (12) mounted on a plate (13) of a watch movement (2) and in which a balance shaft pivots, the balance spring (5) having an inner end fixed to the balance shaft and an outer end fixed to a stud (8) attached to a stud holder (10), the stud holder (10) being pivotally mounted on the cock (12) concentrically with the balance shaft, and means for modifying the active length of the balance spring (5).

Description

Technical field of the invention

[0001] The invention relates to an autonomous adjustment device for the active length of a spiral, for a balance-spiral type oscillator.

[0002] The invention also relates to a watch movement comprising the autonomous adjustment device for the active length of a balance spring and a balance-spring type oscillator.

[0003] The invention further relates to a timepiece, in particular a watch, comprising the watch movement. Technological background

[0004] In the field of watches equipped with mechanical balance-spring type oscillators, there are known mechanisms for manually adjusting the active length of the spring.

[0005] For example, in common manual adjustment mechanisms, the outer end of the balance spring is held in place by a stud attached to a stud holder fixed to a balance cock. A regulator, which rotates relative to the stud holder, is used to adjust the active length of the balance spring, thus allowing adjustment of the balance wheel's frequency. The regulator is a lever, usually with two arms, that pivots centered on the balance staff. One arm of the regulator, for example, carries two pins between which the balance spring is free. A second arm of the regulator can be manually operated to rotate the regulator through a certain angle around the balance staff. This allows the actual position of the counting point to be changed. When the regulator rotates, the active length of the balance spring is shortened or lengthened.However, a drawback of such a manual adjustment system is that gravity influences the frequency of the balance wheel and hairspring oscillations depending on the orientation of the corresponding watch movement. Thus, a watch's rate can vary significantly between its horizontal and vertical positions, for example. Furthermore, when the hairspring moves between the pins due to play between them, the oscillations of the balance wheel and hairspring cause a disturbance in its active length and therefore a slight variation in the frequency of the overall balance wheel and hairspring oscillations.

[0006] To limit the negative effects of gravity, a solution is known, notably from patent document CH 705 605 B1, implementing a device for adjusting the active length of the balance spring. In this device, the regulator incorporates clamping means designed to pinch a terminal portion of the balance spring to define its active length. The outer end of the balance spring is further secured to a fastening system mounted movably relative to the regulator and arranged to cooperate with it. The clamping means, consisting, for example, of a pin-eccentric clamping system in which the terminal portion of the balance spring is pinched, can be loosened or tightened at will by a watchmaker.When the watchmaker loosens the pin-eccentric clamping system, they can move the fixing system using a tool, thus moving the balance spring relative to the fixed regulator and therefore relative to the pin, thereby altering the active length of the balance spring. The watchmaker can then clamp the balance spring against the pin by tightening the clamping system to return the regulating device to its operating position. However, this solution remains a manual adjustment method, which has the drawback of significantly limiting the precision of the adjustment needed to counteract the effects of gravity. Furthermore, this solution is tedious to implement due to the various manual adjustment steps required by the watchmaker.

[0007] Document EP3 502 788 A1 on behalf of the Swatch Group discloses means of modifying the active length of the balance spring according to gravity. Summary of the invention

[0008] The invention therefore aims to provide a device for adjusting the active length of a spiral, for a balance-spring type oscillator, allowing to counterbalance in a simple, precise and autonomous way the effects of gravity, in particular the perturbations of the isochronism of the balance wheel of the oscillator, and overcoming the aforementioned disadvantages of the prior art.

[0009] To this end, the invention relates to an autonomous adjustment device for the active length of a balance spring, for a balance-spring type oscillator, comprising a cock mounted on a plate of a watch movement and in which a balance shaft pivots, the balance spring having an inner end fixed to the balance shaft and an outer end fixed to a stud attached to a stud holder, the stud holder being pivotally mounted on the cock concentrically to the balance shaft, and means for modifying the active length of the balance spring.

[0010] According to the invention, the means for modifying the active length of the spiral include: at least one arm capable of moving between a rest position and a correction position of the device, the at least one arm having a first free end and a second end cooperating with a first pair of pins, the first pair of pins being mounted on the stud holder and angularly offset relative to the stud; a movable weight rotating around a shaft on which at least one cam is mounted, the weight being arranged to rotate freely around the shaft according to gravity, the rotation of the weight causing a rotation of the at least one cam and a displacement of the arm to act on the spiral and simultaneously modify the active length of the spiral; elastic constraint means configured to exert an elastic restoring action in position on the at least one arm;damping means comprising a toothed wheel coaxial with and mounted on the weight, and a damping device arranged to cooperate with the weight via the toothed wheel and limit the change in the active length of the balance spring in the event of sudden acceleration or deceleration.

[0011] In accordance with other advantageous variants of the invention: The device includes a second arm capable of moving between a rest position and a correction position of the device, the second arm having a first free end and a second end cooperating with a second pair of pins, the second pair of pins being mounted on the eyelet holder and angularly offset relative to the eyelet and the first pair of pins; the device includes a second cam arranged to cooperate with the second arm; the cams are radial cams with an external profile; the cams are angularly offset relative to each other; in the rest position of the device, a flat portion of each cam is in contact with an arm, and, in the correction position of the device, a corner or angle of the cam is in contact with one of the arms; the cams are in permanent contact with the free end of each arm regardless of the position of the weight;The free end of the first arm includes elastically deformable adjustment means, the adjustment means being in the form of a spring blade, one end of which is fixed to the arm and the other end is free, the free end being arranged to be subjected to stress and adjust the length of the first arm; the free end of the second arm includes elastically deformable adjustment means, the adjustment means being in the form of a spring blade, one end of which is fixed to the arm and the other end is free, the free end being arranged to be subjected to stress and adjust the length of the second arm; the device includes elastic stress adjustment means, the adjustment means being in the form of a screw, the screw passing through the free end and bearing against the arm;The first pair of pins is fixed to the stud carrier via a first support, the arm being arranged so that it slides between the two pins and comes into contact with the outer coil of the balance spring in the correction position; the second pair of pins is fixed to the stud carrier via a second support, the arm being arranged so that it passes between the two pins and comes into contact with the outer coil of the balance spring in the correction position; the weight is a solid half-disc; the device includes an air damper, the damper being in the form of a body with a cavity of similar shape to that of the weight, the weight being arranged to pivot in the cavity; the device includes a heart-shaped cam mounted on the shaft, the heart-shaped cam being arranged to cooperate with a spring, the assembly forming a device for resetting the position of the first and second arms;The heart-shaped cam is superimposed on the other cams.

[0012] One advantage of the adjustment device according to the invention lies in the fact that it comprises a freely rotating weight that indirectly interacts with a movable arm arranged to act on the outer coil of the balance spring. Rotation of the weight, freely subjected to gravity, causes the arm to move between a rest position and a correction position, and simultaneously acts on the balance spring to modify its active length. This allows the spring to be adjusted to compensate for perturbations in the balance wheel's isochronism caused by gravity. Therefore, the adjustment device according to the invention makes it possible to precisely compensate for the oscillator's rate as a function of its position in space, counterbalancing perturbations in the balance wheel's isochronism caused by gravity, and to do so autonomously.

[0013] The invention also relates to a watch movement comprising the setting device described above, and which includes the features mentioned in dependent claim 17.

[0014] The invention also relates to a timepiece comprising the clock movement described above, and which includes the features mentioned in dependent claim 18.

[0015] Other features and advantages of the present invention will become apparent in the following description of a preferred embodiment, presented by way of non-limiting example with reference to the accompanying drawings. Brief description of the figures

[0016] The purposes, advantages, and characteristics of the device for adjusting the active length of a balance spring, as well as of the watch movement and the timepiece comprising it, will become clearer from the following description based on at least one non-limiting embodiment illustrated by the drawings in which: there figure 1 is a perspective view of a watch movement comprising a device for adjusting the active length of a balance spring according to the invention; the figure 2 an exploded perspective view of the adjustment device figure 1 ; there figure 3 is a top view of the adjustment device of the figure 1 ; there figure 4 is a view from below of the adjustment device of the figure 1 . Detailed description of the invention

[0017] The following description refers to a watch movement equipped with a device for adjusting the active length of a balance spring, for a balance-spring type oscillator. The usual components of a watch movement, which are well known to a person skilled in this technical field, are described only in simplified form or not at all. A person skilled in the art will be able to adapt these various components and make them work together for the operation of the watch movement. In particular, everything concerning the escapement mechanism of the watch movement will not be described hereafter, although such an escapement mechanism could advantageously cooperate with the adjusting device according to the invention.

[0018] There figure 1 represents a part of a timepiece 1, which includes a watch movement 2. In the particular embodiment example of the figure 1The timepiece 1 is a watch. The watch movement 2 comprises an oscillator equipped with a balance wheel 4 and a balance spring 5, and a device 6 for independently adjusting the active length of the balance spring 5. Conventionally, the balance spring 5 is attached to a balance shaft 7 by its inner end (not visible). The balance shaft 7 has one end pivotally mounted in a balance bridge (the latter not shown in the figures for clarity). The outer end of the balance spring 5 is conventionally attached to a stud 8 fixed to a stud holder 10, the stud holder 10 being secured to a balance cock 12 by slight clamping. More precisely, the stud holder 10 is pivotally mounted on the balance cock 12 concentrically with the balance shaft 7, as illustrated in the figure. figure 2 . The shaft 7 of the balance wheel 4 is pivotally mounted in the cock 12.

[0019] The means for modifying the active length of spiral 5 are suitable for modifying the active length of spiral 5 by acting on the length of the outer coil of spiral 5.

[0020] In a particular example of implementation illustrated on the figure 2 , the means for modifying the active length of the spiral 5 comprise at least one arm 60 capable of moving between a rest position and a correction position of the device, the at least one arm having a first free end 600 and a second end 601 cooperating with a first pair of pins 19 forming a guide fork for the arm 60, the first pair of pins 19 being mounted on the stud carrier 10 and offset angularly with respect to the stud 8 via a first support 8'.

[0021] The position of the first support 8' can be modified radially with respect to the stud holder 10. Thus, the second end 601 of the arm 60 can slide between the two pins 19 and comes into contact with the outer coil of the balance spring 5 in the correction position to modify the active length of the balance spring.

[0022] The means for modifying the active length of the balance spring also include a weight 40 that rotates about an axis 41 on which is mounted at least one first cam 31 against which the free end 600 of at least one arm rests. The weight 40 is arranged to rotate about the axis 41 according to the gravity acting upon it, the rotation of the weight 40 causing a rotation of at least one cam 31 and a displacement of at least one arm 60, 61 to act on the outer coil of the balance spring and simultaneously modify the active length of the balance spring.

[0023] The adjustment device 6 further includes damping means comprising a toothed wheel 34 coaxial with the weight 40 and integral with the weight, and a damping device 20 arranged to cooperate with the weight 40 via the toothed wheel 34 and limit the modification of the active length of the spiral 5 in the event of sudden acceleration or deceleration.

[0024] The adjustment device includes elastic constraint means configured to exert an elastic restoring action in position on at least one arm 60. The elastic constraint means are in the form of a rod 62 integral with the arm 60 and a spring blade 63 integral with the eyelet holder 10, the spring blade 61 exerting a restoring force on the rod 62 to exert an elastic restoring action in position on the arm 60.

[0025] Preferably, the adjustment device includes a second arm 61 capable of moving between a rest position and a correction position of the device, the second arm 61 having a first free end 610 and a second end cooperating with a second pair of pins 19' forming a guide fork for the second arm 61, the second pair of pins 19' being mounted on the eyelet holder 10 and offset angularly with respect to the eyelet and the first pair of pins 19 via a second support 8".

[0026] The position of the second support 8" can be modified radially with respect to the stud holder 10. Thus, the second end 611 of the second arm 61 can slide between the two pins 19' and comes into contact with the outer coil of the balance spring in the correction position to modify the active length of the balance spring.

[0027] The engagement means also include a second cam 32 arranged to cooperate with the second arm, the free end of which 610 rests against the second cam 32.

[0028] Elastic constraint means are also associated with the second arm 61, and include a rod 64 integral with the second arm 61 and a spring blade 65 integral with the eyelet holder 10, the spring blade 65 exerting a restoring force on the rod 64 and exerting an elastic restoring action in position on the second arm 61.

[0029] The adjustment device 6 also includes means for adjusting the arms 60, 61, and the free ends 600, 610 of the first and second arms 60, 61, comprising elastically deformable adjustment means for lengthening or shortening the arms. The adjustment means are in the form of a leaf spring, one end of which is fixed to the arm and the other end is free. The free end is arranged to be subjected to tension and to adjust the length of the arms 60, 61, the leaf spring forming a gap between itself and the free end of each arm. Such adjustment is necessary depending on the position of the spiral and the correction required for the spiral.

[0030] The means for modifying the active length of the spiral 5 include two pins 19 fixed to the second pin 8', the second end 601 of the arm 60 being arranged so that it slides between the two pins 19 and comes into contact with the outer coil of the spiral 5 in the correction position and thus modifies the active length of the spiral.

[0031] The means for modifying the active length of the spiral 5 include two further pins 19' fixed to the third pin 8", the second end 611 of the second arm 61 being arranged so that it passes between the two pins 19' and comes into contact with the outer coil of the spiral in the correction position.

[0032] Furthermore, each arm 60, 61 includes means for adjusting the elastic stress. These adjustment means take the form of a screw, the screw passing through the free end of the spring blade and bearing against the arm. Thus, when the screw is tightened, the free end of the blade moves away and the distance between the blade and the free end 600, 610 of arms 60, 61 increases, thereby increasing the length of arms 60, 61. Conversely, when the screw is loosened, the free end of the blade moves towards the free end 600, 610 and the distance between the blade and the free end 600, 610 of arms 60, 61 decreases, thereby increasing the length of arms 60, 61.

[0033] According to a preferred embodiment, the weight 40 is mounted freely for rotation on the axis 41 on which the cams 31, 32 are mounted, such that a rotation of the weight 40 causes a displacement of the arms 60, 61 and simultaneously acts on the means for modifying the active length of the balance spring 5. The displacement of the arms under the effect of the rotation of the weight 40, itself subject to gravity, occurs between a rest position of the device and a correction position of the device, each arm allowing a distinct correction depending on the position of the watch. As illustrated in the figures 1 to 4 For example, the weight 40 is made of a semi-solid disc. In an alternative embodiment not shown in the figures, the weight 40 is made of a solid, two-material disc, the two materials of the disc having distinct densities.

[0034] Thus, depending on the position of the watch movement 2 in space, the weight 40, freely subjected to gravity, can rotate around its axis of rotation and thus cause a displacement of the arms 60, 61. In doing so, this rotation of the weight 40 acts simultaneously on the means of modifying the active length of the balance spring 5, allowing continuous adjustment of the active length of the balance spring in order to compensate for the disturbances of the isochronism of the balance wheel due to gravity.

[0035] To prevent the weight from freewheeling and disrupting the oscillator 4, 5 instead of correcting it, the adjustment device 6 includes damping means comprising a toothed wheel 34 coaxial with and integral to the weight. The damping means include a damping device arranged to cooperate with the weight via the toothed wheel to limit, or even prevent, changes in the active length of the balance spring 5 during sudden acceleration or deceleration.

[0036] As illustrated in the figures, the damping device 20 is in the form of an air damper. The damper comprises a body 22 with a cavity in which a mass 21, similar in shape to the cavity, rotates around an axis 24. The axis 24 also includes a pinion 23 arranged to mesh with the teeth of the gear 34. Thus, when the weight 40 moves, it drives the gear 34, which engages the pinion 23, and rotates the mass 21 of the damping device 20. It is therefore understood that during a rapid movement of the weight 40, the mass 21 will dampen its rotation thanks to the damping device 20. Of course, other types of dampers can be used, such as a mass moving within a cylinder, or even a magnetic damper.

[0037] It will be noted that the shaft 30 carrying the weights 40, the toothed wheel 34 and the cams 31, 32, also includes a third heart-shaped cam 33 fixed to the shaft 30, and superimposed on the cams 31, 32. The third heart-shaped cam 33 is arranged to cooperate with a spring 24, 25 whose end 26 cooperates with the profile of the third heart-shaped cam 33, the whole thus forming a device for resetting the position of the first and second arms 60, 61 to make them return to their rest position naturally.

[0038] In the preferred embodiment in which the device 6 includes two cams 31, 32 for driving the arms 60, 61. The cams 31, 32 are fixed to the shaft 30, angularly offset from each other, and are respectively each in contact with the free end 600, 610 of the arms 60, 61.

[0039] Preferably, each cam 31, 32 is a radial cam with an external profile. Although radial cams with a substantially rectangular external profile are shown on the figures 1 to 4 In practice, the shape envisaged for the external profile of each cam will depend on the type of spiral 5 used and the correction to be applied. For example, a radial cam with a triangular, oblong, or even ovoid external profile can also be used within the framework of the present invention. Preferably, and as shown in the figures 3 and 4 In the rest position of the adjustment device 6, a flat portion of each cam is in contact with an arm 60, 61, while in the correction position of the device 6, a corner or angle of the cam 31, 32 is in contact with the arm 60, 61. Preferably, even more so, as can be seen on the Figures 1 , 3 and 4 , each cam 31, 32 is in contact with its respective arm regardless of the position of the weight 40.

[0040] It is thus understood that, depending on the position of the watch movement 2 in space, the weight 40, freely subject to gravity, can rotate around its axis of rotation and thereby cause a displacement of the arms 60, 61. In doing so, this rotation of the weight 40 simultaneously acts on the means for modifying the active length of the balance spring 5, allowing continuous adjustment of the active length of the balance spring in order to compensate for perturbations in the isochronism of the balance wheel due to gravity. The rotation of the weight 40 causes a rotation of the shaft 30 and has the effect of moving the cams 31, 32, which are fixed to the shaft. The cams then act on the free ends 600, 610 of the arms 60, 61 and move at least one of the arms 60, 61 so that the other end of one of the arms comes into contact with the balance spring 5, thereby modifying the active length of the balance spring 5.

[0041] Once the weight has stabilized following its change of position, the device will return by itself to the rest position thanks to the action of the spring 24, 25 on the third heart-shaped cam 33 which is also attached to the shaft 31.

[0042] The invention also relates to a watch movement 2 comprising a balance-spring type oscillator 4, 5 and an autonomous adjustment device 6 for the active length of the spring 5 as described above.

[0043] The invention also relates to a timepiece 1 comprising a watch movement 2 equipped with a device 6 for autonomously adjusting the active length of the balance spring 5 as described above.

Claims

1. A self-contained device (6) for setting the active length of a balance spring (5), for an oscillator (4, 5) such as a sprung balance, comprising a balance cock (12) designed to be fitted on a plate (13) in a horology movement (2) and in which a balance (4) staff (7) can pivot, the balance spring (5) comprising an internal end designed to be attached to the balance (4) staff (7) and an external end attached to a balance spring stud (8) secured to a balance spring stud holder (10), the balance spring stud holder (10) being fitted so as to pivot on the cock (12) concentrically with the balance (4) staff (7), and means for changing the active length of the balance spring (5), in which the means for changing the active length of the balance spring comprise: - at least a first arm (60) which can move between a locked position and a correction position of the device, the at least first arm (60) having a first free end (600) and a second end (601) engaging with a first pair of pins (19), the first pair of pins (19) being fitted to the balance spring stud holder (10) and angularly offset relative to the balance spring stud (8); - resilient biasing means (62, 63) configured to exert an elastic return-to-position action on the at least a first arm (60); - an inertia block (40) rotationally mobile around an arbor (30) on which at least a first cam (31) is fitted, the inertia block being arranged to turn freely around the arbor as a function of gravity, the rotation of the inertia block (40) causing the at least a first cam (31) to rotate, moving the first arm (60) to act on the balance spring and simultaneously change the active length of the balance spring (5); characterised in that it also comprises: - shock-absorbing means comprising a toothed wheel (34) coaxial with the inertia block (40) and fitted on the inertia block, and a shock-absorbing device (20) arranged to engage with the inertia block via the toothed wheel and limit the change in the active length of the spring (5) in the event of sudden acceleration or deceleration.

2. The self-contained device (6) for setting the active length of a balance spring (5) according to claim 1, characterised in that it comprises a second arm (61) which can move between a locked position and a correction position of the device, the second arm having a first free end (610) and a second end (611) engaging with a second pair of pins (19'), the second pair of pins (19') being fitted to the balance spring stud holder (10) and angularly offset relative to the balance spring stud (8) and to the first pair of pins (19), and second resilient return means (64, 65) configured to exert an elastic return-to-position action on the second arm (61).

3. The self-contained device (6) for setting the active length of a balance spring (5) according to claim 1, characterised in that it comprises a second cam (32) arranged to engage with the second arm (61).

4. The self-contained device (6) for setting the active length of a balance spring (5) according to claim 1 or 3, characterised in that each cam (31, 32) is a radial cam with an external profile.

5. The self-contained device (6) for setting the active length of a balance spring (5) according to claim 3 or 4 when the latter depends from claim 3, characterised in that the cams (31, 32) are angularly offset with respect to each other by an angle greater than 90°.

6. The self-contained device (6) for setting the active length of a balance spring (5) according to any of claims 1 to 5, characterised in that, when the device (6) is in the locked position, a planar portion of each cam (30, 31) is in contact with the respective arm (60, 61) and, when the device (6) is in the correction position, a corner or an angle of the cam (30, 31) is in contact with the respective arm (60, 61)..

7. The self-contained device (6) for setting the active length of a balance spring (5) according to any of claims 1 to 6, characterised in that each cam (30, 31) is in permanent contact with the free end (600, 610) of each respective arm (60, 61) regardless of the position of the inertia block (40, 41).

8. The self-contained device (6) for setting the active length of a balance spring (5) according to any of the preceding claims, characterised in that the free end (600) of the first arm (60) comprises elastically-deformable setting means, the setting means being in the form of a leaf spring with its first end secured to the arm and another end free, the free end being arranged so as to be biased and set the length of the first arm (60).

9. The self-contained device (6) for setting the active length of a balance spring (5) according to any of claims 2, 3 and 4 to 8 when the latter depends from claim 2, characterised in that the free end (610) of the second arm (61) comprises elastically deformable setting means, the setting means being in the form of a leaf spring with its first end secured to the arm and another end free, the free end being arranged to be biased and set the length of the second arm (61).

10. The self-contained device (6) for setting the active length of a balance spring (5) according to any of the preceding claims, characterised in that it comprises means for setting the elastic bias, the setting means being in the form of a screw, the screw running through the free end and bearing against the arm.

11. The self-contained device (6) for setting the active length of a balance spring (5) according to any of the preceding claims, characterised in that the first pair of pins (19) is fastened to the balance spring stud holder (10) via a first support (8'), the first arm (60) being arranged so that it slides between the first two pins (19) and comes into contact with the outer coil of the balance spring in the correction position.

12. The self-contained device (6) for setting the active length of a balance spring (5) according to claims 2 to 11, when they depend from claim 2, characterised in that the second pair of pins (19') is fastened to the balance spring stud holder (10) via a second support (8"), the second arm (61) being arranged so that it runs between the two pins (19) and comes into contact with the outer coil of the balance spring in the correction position.

13. The self-contained device (6) for setting the active length of a balance spring (5) according to any of the preceding claims, characterised in that the inertia block (21) is a solid half-disc.

14. The self-contained device (6) for setting the active length of a balance spring (5) according to any of the preceding claims, characterised in that the device comprises an air damper, the damper being in the form of a body with a cavity similar in shape to that of the inertia block, the inertia block being arranged to pivot in the cavity.

15. The self-contained device (6) for setting the active length of a balance spring (5) according to any of claims 3 or its dependents, characterised in that it comprises a third, heart-shaped cam (33) fitted on the arbor (30), the third, heart-shaped cam being arranged to engage with a spring (24, 25), the assembly forming a zero reset device for the position of the first and second arms (60, 61).

16. The self-contained device (6) for setting the active length of a balance spring (5) according to the preceding claim, characterised in that the third, heart-shaped cam (33) is superimposed on the first and second cams (31, 32).

17. A horology movement (2) comprising an oscillator (4, 5) such as a balance spring and a self-contained device (6) for setting the active length of the balance spring (5), characterised in that the self-contained setting device (6) is according to any of the preceding claims.

18. A timepiece (1) comprising a horology movement (2), characterised in that the horology movement (2) is in accordance with claim 17.

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