Device with regulating member for timepiece

Abstract

The invention relates to a regulating organ device for a timepiece comprising a frame (2) and a regulating organ (3). The regulating organ (3) comprises a balance (8) secured to a shaft (9) and first and second balance springs (10, 11). Each of the first and second balance springs (10, 11) has an inner end secured to one of the shaft (9) and the frame (2) and an outer end secured to the other of the shaft (9) and the frame (2). The shaft (9) comprises pivots (14, 15) arranged to rotate in bearings (16, 17) of the frame (2). The first and second balance springs (10, 11) are prestressed so as to exert on the shaft (9), parallel to the shaft (9), two forces in opposite directions.

Description

[0001] The present invention relates to a balancing-spring type regulating organ for a timepiece and more precisely to a device, such as a movement, a part of a movement or a tourbillon or carousel, comprising such a regulating organ.

[0002] In a timepiece, the regulating organ is the time base that regulates the rotation of the gear train. The regulating organ generally comprises a balance wheel, that is to say an oscillating inertial organ, associated with a spiral return spring called a "hairspring" which tends to return the balance wheel to a position of equilibrium. The balance wheel is integral with a shaft which is supported at its two ends by bearings. The inner end of the hairspring is fixed to the shaft by means of a collet and its outer end is fixed to the frame which carries the bearings, a frame which is generally fixed but which is mobile in the case of the tourbillon or carousel. Depending on the direction of rotation of the balance wheel during its oscillations, the hairspring contracts or expands, always seeking to return to its rest position corresponding to the equilibrium position of the balance wheel. Most often, the hairspring is flat.Its last coil may nevertheless end with a curve that leaves the plane of the balance spring and is shaped so that the center of gravity of the balance spring remains substantially on the balance wheel axis during the oscillations of the regulating organ in order to make the deformations of the balance spring concentric, the balance spring is then called a "Breguet balance spring". There are also balance springs that at rest are not flat but cylindrical, conical or spherical. In the case of a completely flat balance spring, it is not necessarily shaped like an Archimedean spiral. It may have a variable pitch, a variable section or one or more terminal curves to limit the displacement of the center of gravity of the balance spring during the oscillations of the regulating organ and make the deformations of the balance spring concentric.

[0003] An important characteristic of a regulating organ is its quality factor, namely the ratio between the stored energy and the dissipated energy during an oscillation period. A regulating organ with a high quality factor requires less energy to maintain its oscillations at a given oscillation amplitude. One way to increase the quality factor is to reduce the friction of the shaft pivots in the bearings. This can be achieved, for example, by using special materials with a very low friction coefficient or by modifying the geometry of the components to reduce the size of the contacting surfaces. US Patent 3,186,157 describes another solution, in which the balance is associated with two flat balance springs, one on each side of the balance, which are strong enough not only to perform their elastic return function but also to suspend the balance axially and thus reduce friction in the bearings.However, this solution, proposed more particularly for electric watches whose oscillations of the regulating organ are fast and small, is disadvantageous in the case of mechanical watches. In a mechanical watch, in fact, the oscillation frequency is much lower and the oscillation amplitude much greater so that to maintain a given oscillation frequency and amplitude the strengthening of the balance spring (increase in its dimensions or its Young's modulus) will have to be compensated by an increase in the inertia of the balance wheel and by an increase in the power supplied to maintain the oscillations, which is contrary to the desired goal.

[0004] In its introductory part, US patent 3186157 mentions the existence in the state of the art of another solution for reducing friction in the bearings, namely suspending the balance wheel by a magnetic device or a helical spring. The disadvantage of a magnetic device is that it can disrupt the operation of the timepiece because several of its components are sensitive to magnetism. As for the helical spring, it is not described.

[0005] The present invention aims to propose a device with a regulating organ in which the quality factor of the regulating organ is improved by a mechanical solution other than that consisting of increasing the force of the balance spring(s), and more precisely by a mechanical solution compatible with the oscillation frequencies and amplitudes found in mechanical timepieces.

[0006] To this end, the invention relates to a device with a regulating member according to claim 1, particular embodiments being defined in the dependent claims.

[0007] The invention further provides a timepiece, in particular a mechanical timepiece, comprising such a regulating member.

[0008] Other characteristics and advantages of the present invention will appear on reading the following detailed description made with reference to the appended drawings in which: there figure 1 is a perspective view of a part of a regulating member device according to the invention; figure 2 is a side view of said part of the regulating member device according to the invention; figure 3 is a perspective view of the regulating member of the device according to the invention; figure 4 is a side view of the regulating member of the device according to the invention.

[0009] In reference to the figures 1 to 4 , a regulating member device 1 according to the invention for a timepiece such as a watch, in particular a wristwatch, and more particularly for a mechanical timepiece, comprises a frame 2 and a regulating member 3 mounted on or in the frame 2. In the example shown, the frame 2 is that of the movement of the timepiece and therefore constitutes a fixed part of the timepiece. The frame 2 comprises a plate 4 supporting the moving components of the movement and having a through opening 5 in which the regulating member 3 is located. The frame 2 further comprises bridges fixed to the plate 4, in particular two balance bridges 6, 7, each in the form of a bar or arm, one fixed on the upper side of the plate 4 and the other on the lower side of the plate 4 and extending above and below the through opening 5 respectively.

[0010] The regulating member 3 comprises a balance 8 mounted securely on a shaft 9 and two balance springs 10, 11 arranged on either side of the balance 8 and fixed to the shaft 3 by their inner end, by means of respective collets 12, 13. The balance 8, the shaft 9 and the balance springs 10, 11 have a common geometric axis A which constitutes the axis of rotation of the balance 8 - shaft 9 - collets 12, 13 assembly in operation. The two ends of the shaft 9, namely its pivots 14, 15, are arranged to rotate in respective bearings 16, 17 located in the two balance bridges 6, 7. In addition to the bearing 16, 17, each balance bridge 6, 7 comprises a stud holder (of which only one 18 is visible in the drawings) arranged to accommodate, in a conventional manner per se, a stud 20, 21 to which the outer end of the corresponding balance spring 10, 11 is fixed. Each balance spring 10, 11 is thus coupled by its inner end to the shaft 9 and by its outer end to the frame 2.

[0011] The shaft 9 also securely carries a double balance wheel 22, on which projects a wheel pin 23 intended to cooperate in a conventional manner with an escapement anchor for maintaining the oscillations of the balance wheel 8.

[0012] According to the invention, the balance springs 10, 11 are axially prestressed, by positions distant from the inner end and the outer end of each balance spring 10, 11 along the axis A, so that two forces parallel to the axis A and in opposite directions are exerted on the shaft 9 by the balance springs 10, 11. In certain exemplary embodiments, the prestressing of each balance spring 10, 11 is obtained by moving its inner and outer ends away from each other along the axis A, relative to the state of rest of the balance spring, by a distance greater than or equal to the height of a turn of the balance spring 10, 11, preferably greater than or equal to the height of several turns of the balance spring 10, 11.In some embodiments, the prestressing of each balance spring 10, 11 is obtained by moving its inner and outer ends away from each other along the axis A, relative to the state of rest of the balance spring, by a distance greater than or equal to 0.1 mm, preferably greater than or equal to 0.2 mm, preferably greater than or equal to 0.5 mm, preferably greater than or equal to 1 mm, preferably greater than or equal to 1.5 mm. Typically, the balance springs 10, 11 each have a convex shape when coupled to the shaft 9 and the frame 2, the two convex shapes preferably being portions of a sphere and preferably being symmetrical to each other relative to a plane perpendicular to the axis A, as can be seen in the drawings.

[0013] Before their assembly with the shaft 9 and the frame 2, the hairsprings 10, 11 may be completely flat hairsprings, Breguet hairsprings (flat hairsprings with a terminal curve called "Phillips" coming out of the plane of the hairspring to approach the axis of rotation and bring back and maintain the center of gravity of the hairspring on the axis of rotation), or other. According to a particularly advantageous example, corresponding to that illustrated in the drawings, the hairsprings 10, 11 before their assembly with the shaft 9 and the frame 2 are flat hairsprings with a terminal Phillips curve which differ from the Breguet hairsprings in that the lifting of the Phillips curve out of the plane of the hairspring is obtained solely by an elastic deformation of the hairspring, that is to say without a plastic deformation bend, like the Phillips curves of cylindrical hairsprings.Indeed, the axial separation of the inner and outer ends of each spiral 10, 11 after the assembly of the latter with the shaft 9 and the frame 2 makes it possible to avoid any contact between the Phillips curve and the turns in the axial direction despite the absence of a bend raising the Phillips curve. Doing without a plastic deformation bend has the advantage of not disturbing the mechanical properties of the spiral, in particular the stiffness and the elastic limit.

[0014] In the example shown, the hairspring 10 is stretched axially by the preload to pull the shaft 9 towards the upper balance bridge 6, and the hairspring 11 is stretched axially by the preload to pull the shaft 9 towards the lower balance bridge 7. A reverse configuration is however possible where the positions of the inner end and the outer end of each hairspring 10, 11 along the axis A would be reversed - for this purpose each balance bridge 6, 7 could have an arm which would extend to a point close to the balance 8 in order to fix the outer end of the hairspring 10, 11 to the frame 2 at this point -, and where therefore the axial stretching of the hairspring 10 would have the effect of pulling the shaft 9 towards the lower balance bridge 7 and the axial stretching of the hairspring 11 would have the effect of pulling the shaft 9 towards the upper balance bridge 6.

[0015] The two forces in opposite directions exerted by the balance springs 10, 11 on the shaft 9 make it possible to axially suspend the latter, at least partially, and thus to eliminate or reduce the axial bearing force of the pivots 14, 15 in the bearings 16, 17 and the resulting friction, this thanks to the balance which is created between these two forces and the axial bearing force of the pivots 14, 15 in the bearings 16, 17. The greater the two forces in opposite directions exerted by the balance springs 10, 11 on the shaft 9, the smaller the axial bearing force of the pivots 14, 15 in the bearings 16, 17. Said two forces in opposite directions can have the same intensity, for example by being produced by identical balance springs 10, 11, but can also have different intensities.

[0016] Compared to traditional hairsprings, hairsprings with terminal curve(s) such as, for example, hairsprings 10, 11 with Phillips curve illustrated in the drawings, Breguet hairsprings or completely flat hairsprings of the type described in patent CH 697207 or EP 2138912, have the advantage of deforming concentrically and, consequently, of reducing the radial support forces of the pivots in the bearings and the resulting friction regardless of the angular orientation of the hairsprings relative to each other. For this reason, these hairsprings are preferred in the present invention. Hairsprings 10, 11 may nevertheless be traditional hairsprings, without terminal curves making their deformations concentric.In this case, however, they are preferably wound in opposite directions, or are angularly offset by 180° relative to each other, so that the respective radial forces they exert on the shaft 9 due to their eccentric deformations compensate each other, thus reducing the radial bearing forces of the pivots 14, 15 in the bearings 16, 17 and the resulting friction.

[0017] The present invention has been described above by way of example only. It is understood that modifications could be made without departing from the scope of the claimed invention. For example, instead of constituting a fixed part of the timepiece, the frame 2 could be a mobile frame, for example the cage of a tourbillon or carousel in which the shaft 9 and the balance 8 would be axially suspended by the balance springs 10, 11. Another modification could consist of coupling the inner end of the balance springs 10, 11 to the frame 2 rather than to the shaft 9 and coupling the outer end of the balance springs 10, 11 to the balance 8 rather than to the frame 2. Finally, although it is preferable, for reasons of arrangement, that the balance springs 10, 11 are arranged on either side of the balance 8, they could be located on the same side of the balance 8 as long as they exert on the shaft 9, parallel to the shaft 9, directly or indirectly, two forces of opposite directions.

Claims

1. A regulating organ device for a timepiece comprising a frame (2) and a regulating organ (3), the regulating organ (3) comprising a balance (8) secured to a shaft (9) and first and second balance springs (10, 11), each of the first and second balance springs (10, 11) having an inner end secured to one of the shaft (9) and the frame (2) and an outer end secured to the other of the shaft (9) and the frame (2), the shaft (9) having pivots (14, 15) arranged to rotate in bearings (16, 17) of the frame (2), characterized in that the first and second spirals (10, 11) are prestressed so as to exert on the shaft (9), parallel to the shaft (9), two forces of opposite directions.

2. Device according to claim 1, characterized in that the first and second balance springs (10, 11) are arranged on either side of the balance wheel (8).

3. Device according to claim 1 or 2, characterized in thatthe inner end of each of the first and second spirals (10, 11) is secured to the shaft (9) and the outer end of each of the first and second spirals (10, 11) is secured to the frame (2).

4. Device according to one of claims 1 to 3, characterized in that each of the first and second prestressed spirals (10, 11) has a convex shape.

5. Device according to claim 4, characterized in that the convex shape of each of the first and second prestressed spirals (10, 11) is a portion of a sphere shape.

6. Device according to claim 4 or 5, characterized in that the convex shape of the first spiral (10) and that of the second spiral (11) are symmetrical with respect to a plane perpendicular to the shaft (9).

7. Device according to one of claims 1 to 6, characterized in that each of the first and second spirals (10, 11) is a spiral with concentric deformations.

8. Device according to one of claims 1 to 7, characterized in that each of the first and second spirals (10, 11) is a flat spiral with a Phillips curve to which the prestress has given a convex shape.

9. Device according to claim 8, characterized in that each of the first and second spirals (10, 11) is without plastic deformation bend between the Phillips curve and the rest of the spiral.

10. Device according to one of claims 1 to 6, characterized in that the first and second spirals (10, 11) are wound in opposite directions or are offset by 180° so that the respective radial forces which they exert on the shaft (9) due to eccentric deformations of these spirals (10, 11) during the oscillations of the regulating member (3) compensate each other.

11. Device according to one of claims 1 to 10, characterized in that it consists of a clockwork movement.

12. Device according to one of claims 1 to 10, characterized in thatIt consists of a whirlwind or carousel.

13. Timepiece comprising a device according to one of claims 1 to 12.

14. Mechanical timepiece comprising a device according to one of claims 1 to 12.

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