DEVICE FOR AUTONOMOUSLY ADJUSTING THE ACTIVE LENGTH OF A BALANCE SPRING

Abstract

A device (6) for autonomously adjusting the active length of a balance spring (5), for an oscillator (4, 5) of the sprung balance type, including a cock (12) mounted on a plate (13) of a horological movement (2) and in which cock a balance staff pivots, the balance spring (5) including an inner end integral with the balance staff and an outer end integral with a first stud (8) fastened to a stud-holder (10), the stud-holder (10) being pivotally mounted on the cock (12) concentrically with the balance staff, and means for modifying the active length of the balance spring (5).

Claims

1. A device (6) for autonomously adjusting the active length of a balance spring (5), for an oscillator (4, 5) of the sprung balance type, comprising a cock (12) mounted on a plate (13) of a horological movement (2) and in which cock a staff (7) of the balance (4) pivots, the balance spring (5) including an inner end integral with the staff (7) of the balance (4) and an outer end integral with a first stud (8) fastened to a stud-holder (10), the stud-holder (10) being pivotally mounted on the cock (12) concentrically with the staff (7) of the balance (4), and means for modifying the active length of the balance spring (5); wherein the means for modifying the active length of the balance spring comprise: a lever (60) capable of pivoting on the stud-holder (10) between a rest position and two correction positions of the device, the lever (60) having a first free end (600) and a second end (601) having two beaks (601, 602); resilient stressing means (70, 71, 72, 73) configured to exert a resilient restoring action on the lever (60); an inertia block (40) rotatable about a shaft (30) on which a cam (31) is mounted, the inertia block being arranged to rotate freely about the shaft as a function of gravity, the rotation of the inertia block (40) rotating the cam (31) and pivoting the lever (60) so that one of the beaks (601, 602) acts on the balance spring and simultaneously modifies the active length of the balance spring (5); and damping means comprising a toothed wheel (34) coaxial with the inertia block (40) and mounted on the inertia block, and a damping device (20) arranged to cooperate with the inertia block via the toothed wheel and to limit the change in the active length of the balance spring (5) in the event of sudden acceleration or deceleration.

2. The device (6) for autonomously adjusting the active length of a balance spring (5) according to claim 1, wherein the stud-holder (10) comprises an extension (100) provided with an opening (101) through which passes a pivot pin (102) for the lever (60).

3. The device (6) for autonomously adjusting the active length of a balance spring (5) according to claim 2, wherein the lever comprises, at its second end (600), a ball bearing (603) through which the pivot pin (102) passes.

4. The device (6) for autonomously adjusting the active length of a balance spring (5) according to claim 2, wherein the opening (101) is oblong in shape in order to be able to adjust the position of the lever (60) relative to the balance spring (5).

5. The device (6) for autonomously adjusting the active length of a balance spring (5) according to claim 1, wherein the resilient stressing means (70, 71, 72) configured to exert a resilient restoring action on the lever are integral with the plate (13).

6. The device (6) for autonomously adjusting the active length of a balance spring (5) according to claim 1, wherein the resilient stressing means (73) configured to exert a resilient restoring action on the lever are integral with the stud-holder (10).

7. The device (6) for autonomously adjusting the active length of a balance spring (5) according to claim 1, wherein the cam (31) is a radial cam with an external profile.

8. The device (6) for autonomously adjusting the active length of a balance spring (5) according to claim 1, wherein, when the device (6) is in the rest position, a flat portion of the cam (31) is in contact with the lever (60), and when the device (6) is in the correction position, a corner or angle of the cam (31) is in contact with the lever (60).

9. The device (6) for autonomously adjusting the active length of a balance spring (5) according to claim 1, wherein the cam (31) is in permanent contact with the free end (610) of the lever (60) whatever the position of the inertia block (40).

10. The device (6) for autonomously adjusting the active length of a balance spring (5) according to claim 1, wherein the inertia block (21) is a solid half-disc.

11. The device (6) for autonomously adjusting the active length of a balance spring (5) according to claim 1, wherein the device comprises an air damper, the damper being in the form of a body with a cavity of similar shape to that of the inertia block, the inertia block being arranged to pivot in the cavity.

12. The device (6) for autonomously adjusting the active length of a balance spring (5) according to claim 1, further comprising a heart-shaped cam (32) mounted on the shaft (30), the heart-shaped cam being arranged to cooperate with a spring (24, 25), the assembly forming a device for resetting the position of the lever (60).

13. The device (6) for autonomously adjusting the active length of a balance spring (5) according to claim 12, wherein the heart-shaped cam (32) is superimposed on the cam (31).

14. A horological movement (2) including an oscillator (4, 5) of the sprung balance type and the device (6) for autonomously adjusting the active length of the balance spring (5) in accordance with claim 1.

15. A timepiece (1) including the horological movement (2) in accordance with claim 14.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0032] 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:

[0033] FIG. 1 is a top perspective view of a horological movement of a watch comprising a device for adjusting the active length of a balance spring according to a first embodiment of the invention;

[0034] FIG. 2 is a top perspective view of a horological movement of a watch comprising a device for adjusting the active length of a balance spring according to a first embodiment of the invention;

[0035] FIG. 3 is a top perspective view of the adjustment device of FIG. 1 according to the first embodiment of the invention;

[0036] FIG. 4 is an exploded perspective view of the adjustment device of FIG. 1 according to the first embodiment of the invention;

[0037] FIGS. 5a and 5b are top and exploded perspective views respectively of the adjustment device of FIG. 1 according to a second embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0038] 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.

[0039] FIG. 1 shows part of a timepiece 1, which includes a horological movement 2. In the particular example embodiment shown in FIG. 1, the timepiece 1 is a watch. The horological movement 2 includes an oscillator equipped with a balance 4 and a balance spring 5, and a device 6 for autonomously adjusting the active length of the balance spring 5. Conventionally, the balance spring 5 is fastened to a staff 7 of the balance 4 by its inner end (not visible). The staff 7 of the balance 4 has one end pivotally mounted in a balance bridge (the latter is not visible in the figures for the sake of clarity). The outer end of the balance spring 5 is fastened in the conventional way to a stud 8 fastened to a stud-holder 10, the stud-holder 10 being made integral with a cock 12 by light clamping. More specifically, the stud-holder 10 is pivotally mounted on the cock 12 concentrically with the staff 7 of the balance 4, as shown in FIG. 2. The staff 7 of the balance 4 is pivotally mounted in the cock 12.

[0040] 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 FIGS. 1 to 4 and in FIGS. 5a and 5b respectively, the means for modifying the active length of the balance spring 5 include a lever 60 capable of moving between a rest position and two correction positions of the device. The lever has a first free end 610 and a second end 600 provided with two beaks 601, 602, each beak 601, 602 being arranged to act independently of the other on the outer coil of the balance spring and to modify the active length of the balance spring.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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 FIGS. 1 to 4, the strip-spring 70 comprises a first end 71 in contact with the free end 610 of the lever 60 so as to hold the free end 610 against the profile of the cam 31, and a second end integral with the plate 13. According to the second embodiment illustrated in FIGS. 5a and 5b, the strip-spring 73 is integral with the stud-holder 10 and further allows the free end 610 to be pressed against the profile of the cam 31.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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 FIGS. 1 to 5b, in practice the shape envisaged for the external profile of the cam will depend on the type of balance spring 5 used and the correction to be made thereto. For example, a radial cam with a triangular, oblong or ovoid external profile can also be used in the context of the present invention. Preferably, when the adjustment device 6 is in the rest position, a flat portion of the cam is in contact with the free end 610 of the lever 60, whereas when the device 6 is in the correction position, a corner or angle of the cam 31 is in contact with the free end 610 of the lever 60. Even more preferably, the cam 31 is in contact with the lever 60 whatever the position of the inertia block 40.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.