Patent Application
20240302797
This application is claiming priority based on European Patent Application No. 23160132.9 filed on Mar. 6, 2023.
The invention relates to a device for autonomously adjusting the active length of a balance spring, for an oscillator of the sprung balance type.
The invention further relates to a horological movement including the device for autonomously adjusting the active length of a balance spring and an oscillator of the sprung balance type.
The invention further relates to a timepiece, in particular a watch, including the horological movement.
In watches fitted with mechanical oscillators of the sprung balance type, mechanisms for manually adjusting the active length of the balance spring are known.
For example, in regular manual adjustment mechanisms, the outer end of the balance spring is immobilised by a stud fastened to a stud-holder integral with a cock. An index that can rotate relative to the stud-holder is provided to adjust the active length of the balance spring, thereby allowing the frequency of the sprung balance to be adjusted. The index is a pivoting lever, typically provided with two arms, centred on the coordinate of the balance staff. A first arm of the index carries, for example, two pins between which the balance spring is free. A second arm of the index can be manually operated to rotate the index through a certain angle about the balance staff. This allows the actual position of the counting point to be changed. As the index rotates, the active length of the balance spring reduces or increases. However, one drawback of such a manual adjustment device is that the earth's gravity influences the oscillation frequency of the sprung balance depending on the orientation of the corresponding horological movement. As a result, the rate of a watch can vary significantly, in particular between its horizontal and vertical positions. Moreover, when the balance spring moves between the pins due to the play therebetween, the oscillations of the sprung balance alter its active length and thus cause a slight variation in the oscillation frequency of the sprung balance assembly.
In order to limit the negative effects of gravity, one solution known in particular from patent CH 705 605 B1, implements a device for adjusting the active length of the balance spring, wherein the index carries clamping means designed to clamp an end portion of the balance spring in order to define the active length thereof. The outer end of the balance spring is also integral with a fastening system movably mounted relative to the index and arranged to cooperate therewith. The clamping means, consisting for example of a pin/eccentric clamping system wherein the end portion of the balance spring is clamped, can be loosened or tightened at will by a watchmaker. Once the watchmaker has loosened the pin/eccentric clamping system, the fastening system can be moved using a tool, thus allowing the balance spring to be moved relative to the index, which remains stationary, and thus relative to the pin, thus allowing the active length of the balance spring to be modified. The watchmaker can then clamp the balance spring against the pin by tightening the clamping system, to return the adjustment device to its operating position. However, such a solution remains a manual adjustment solution, which has the drawback of considerably limiting the precision of the adjustment used to offset the effects of gravity. Moreover, such a solution is tedious to implement, due to the various manual adjustment steps to be carried out by a watchmaker to make the adjustment.
The purpose of the invention is thus to provide a device for adjusting the active length of a balance spring, for an oscillator of the sprung balance type, making it possible to offset the effects of gravity, in particular disturbances to the isochronism of the balance of the oscillator, in a simple, precise and autonomous manner, and compensating for the above-mentioned drawbacks of the prior art.
To this end, the invention relates to a device for autonomously adjusting the active length of a balance spring, for an oscillator of the sprung balance type, comprising a cock mounted on a plate of a horological movement and in which cock a balance staff pivots, the balance spring having an inner end integral with the balance staff and an outer end integral with a first stud fastened to a stud-holder, the stud-holder being pivotably mounted on the cock concentrically with the balance staff, and means for modifying the active length of the balance spring.
According to the invention, the means for modifying the active length of the balance spring comprise:
In accordance with other advantageous alternative embodiments of the invention:
One advantage of the adjusting device according to the invention lies in the fact that it comprises an inertia block mounted so as to rotate freely and cooperating indirectly with a movable arm arranged to act on the outer coil of the balance spring. Rotation of the inertia block, which is freely subject to gravity, thus causes the arm to move between a rest position and a correction position of the device, and simultaneously acts on the balance spring to modify the active length of the balance spring, allowing the latter to be adjusted in order to compensate for disturbances to the isochronism of the balance due to gravity. As a result, the adjustment device according to the invention allows the oscillator's rate to be precisely compensated for as a function of its position in space, by offsetting the disturbances to the isochronism of the balance due to gravity, in an autonomous manner.
The invention further relates to a horological movement including the adjustment device described above, and which includes the features mentioned in dependent claim 14.
The invention further relates to a timepiece including the horological movement described above, and which includes the features mentioned in dependent claim 15.
Further features and advantages of the present invention will become apparent from the following description of a preferred embodiment, given by way of a non-limiting example with reference to the accompanying drawings.
The purposes, advantages and features of the device for adjusting the active length of a balance spring, and of the horological movement and timepiece comprising it, will become clearer in the following description which is given on the basis of at least one non-limiting embodiment illustrated by the drawings in which:
In the following description, reference is made to a horological movement equipped with a device for adjusting the active length of a balance spring, for an oscillator of the sprung balance type. The usual components of the horological movement, which are well known to a person skilled in the art, 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 cooperate for the operation of the horological movement. In particular, everything relating to the escapement mechanism of the horological movement will not be described below, although such an escapement mechanism can advantageously cooperate with the adjustment device according to the invention.
The means 6 for modifying the active length of the balance spring 5 are capable of modifying the active length of the balance spring 5 by acting on the length of the outer coil of the balance spring 5. In the two example embodiments illustrated in
As can be seen from the figures, the stud-holder 10 comprises an extension 100 provided with an opening 101 through which passes a pivot pin 102 about which the lever 60 pivots to move from its rest position to a correction position.
In order to pivot about the pivot pin 102 which is formed by a bolt 103 and a nut 104, the lever comprises, at its second end 600, a ball bearing 603 through which the shank of the bolt 103 passes.
It should also be noted that the opening 101 is oblong in shape so that the position of the lever 60 can be adjusted relative to the balance spring 5. Once the correct position of the lever has been determined, the second end 600 of the lever simply needs to be fastened to the extension 100 of the stud-holder by tightening the bolt 103 and the nut 104.
The means 6 for modifying the active length of the balance spring further comprise an inertia block 40 which can rotate about a shaft 30 on which is mounted a cam 31 against which the free end 610 of the lever 60 rests. The inertia block 40 is arranged so that it can rotate about the shaft 30 as a function of the gravity to which it is subjected, the rotation of the inertia block 40 rotating the cam 31 and moving the lever 60 to act on the outer coil of the balance spring 5 and simultaneously modify the active length of the balance spring.
The adjustment device 6 further comprises damping means comprising a toothed wheel 34 coaxial with the inertia block 40 and integral with the inertia block, and a damping device 20 arranged to cooperate with the inertia block 40 via the toothed wheel 34 and to limit the change in the active length of the balance spring 5 in the event of sudden acceleration or deceleration.
The adjustment device comprises resilient stressing means configured to exert a resilient restoring action on the at least one arm 60. The resilient stressing means take the form of a strip-spring 70, 73. According to the first embodiment illustrated in
The means for modifying the active length of the balance spring 5 include two pins 19 fastened to the second stud 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 balance spring 5 in the correction position and thus modifies the active length of the balance spring.
The inertia block 40 is mounted so as to rotate freely on the shaft 30 on which the cams 31 are mounted, so that rotation of the inertia block 40 causes the lever 60 to move and simultaneously acts on the means for modifying the active length of the balance spring 5. The lever moves under the effect of the rotation of the inertia block 40, which is itself subject to gravity, between a rest position of the device and two correction positions of the device, the beaks 601, 602 of the lever 60 allowing a distinct correction to be made depending on the position of the watch. As illustrated in the figures, the inertia block 40 consists for example of a half-full disc. In an alternative embodiment not shown in the figures, the inertia block 40 consists of a solid bi-material disc, the two materials of the disc having different densities.
Thus, depending on the position of the horological movement 2 in space, the inertia block 40, which is freely subject to gravity, can rotate about its axis of rotation and thus cause the lever 60 to move. In so doing, the rotation of the inertia block 40 simultaneously acts on the means for modifying the active length of the balance spring 5, allowing the active length of the balance spring to be continuously adjusted in order to compensate for disturbances to the isochronism of the balance due to gravity.
In order to prevent the inertia block from forming a loose wheel and upsetting the oscillator 4, 5 instead of correcting it, the adjustment device 6 comprises damping means comprising a toothed wheel 34 coaxial with the inertia block and integral therewith. The damping means comprise a damping device arranged to cooperate with the inertia block via the toothed wheel to limit, or even prevent, the modification of the active length of the balance spring 5 during sudden acceleration or deceleration.
As illustrated in the figures, the damping device 20 is in the form of an air damper, the damper comprising a body 22 with a cavity in which a weight 21 of similar shape to the cavity rotates about a shaft 24. The shaft 24 further includes a pinion 23 arranged to cooperate with the toothing of the toothed wheel 34. Thus, when the inertia block 40 moves, it drives the toothed wheel 34 which meshes with the pinion 23, and causes the weight 21 of the damping device 20 to rotate. It is thus understood that when the inertia block 40 moves considerably, the weight 21 will brake the rotation of the inertia block 40 thanks to the damping device 20. It goes without saying that other types of damper can be used, such as a weight moving in a cylinder, or a magnetic damper.
It should be noted that the shaft 30 carrying the inertia block 40, the toothed wheel 34 and the cam 31, further comprises a heart-shaped cam 32 integral with the shaft 30, and superimposed on the cam 31. The heart-shaped cam 32 is arranged to cooperate with a spring 24, 25, the end 26 of which cooperates with the profile of the heart-shaped cam 32, the assembly thus forming a device for resetting the position of the lever 60 to return it to its natural rest position when the inertia block is no longer subject to gravity.
Preferably, the cam 31 is a radial cam with an external profile. Although a radial cam with a substantially rectangular external profile is shown in
It is thus conceivable that, depending on the position of the horological movement 2 in space, the inertia block 40, which is freely subject to gravity, can rotate about its axis of rotation and thus cause the lever 60 to move. In so doing, this rotation of the inertia block 40 simultaneously acts on the means for modifying the active length of the balance spring 5, making it possible to continuously adjust the active length of the balance spring in order to compensate for disturbances to the isochronism of the balance due to gravity. Rotation of the inertia block 40 rotates the shaft 30 and causes the cam 31 which is integral with the shaft 30 to move, the cam then acting on the free end 610 of the lever 60 and moving the latter so that the second end 600 of the lever pivots about the pivot pin 102 and so that one of the beaks 601, 601 comes into contact with the balance spring 5 so as to modify the active length of the balance spring.
Once the inertia block has stabilised following its change of position, the device will return to its rest position by itself thanks to the action of the spring 24, 25 on the heart-shaped cam 32, which is also integral with the shaft 30.
The invention further relates to a horological movement 2 including an oscillator 4, 5 of the sprung balance type and a device 6 for autonomously adjusting the active length of the balance spring 5 as described above.
The invention further relates to a timepiece 1 comprising a horological movement 2 equipped with a device 6 for autonomously adjusting the active length of the balance spring 5 as described above.
| Number | Date | Country | Kind |
|---|---|---|---|
| 23160132.9 | Mar 2023 | EP | regional |
