Device with a regulating member for timepiece

Abstract

To provide a device with a regulating member in which a quality factor of the regulating member is improved by a mechanical solution.SOLUTION: The invention relates to a device with a regulating member for a timepiece comprising a frame (2) and a regulating member (3). The regulating member (3) comprises a balance (8) fixedly attached to a staff (9), and first and second balance springs (10, 11). Each of the first and second balance springs (10, 11) has an inner end fixedly attached to one of the staff (9) and frame (2), and an outer end fixedly attached to the other of the staff (9) and frame (2). The staff (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 preloaded so as to exert on the staff (9), parallel to the staff (9), two forces of opposite directions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a regulating element of the sprung balance type for a timepiece, and more precisely to a movement, a movement part or a device such as a tourbillon or a carousel, comprising such a regulating element. [Background technology]

[0002] In a watch, the regulating element is the time base that sets the rotational speed of the hour-going train. It generally includes a balance, i.e., a periodically oscillating inertia element, accompanied by a helical return spring called a "balance spring" that attempts to return the balance to its equilibrium position. The balance is fixed to a staff supported at both ends by bearings. The balance spring's inner end is fixed to the staff via a collet, and its outer end is fixed to a frame that carries the bearings. The frame is generally stationary, but in the case of a tourbillon or carousel, it is movable. Depending on the direction of rotation of the balance during oscillation, the balance spring contracts or expands, always attempting to return to a rest position corresponding to the balance's equilibrium position. In most cases, the balance spring is flat. However, its last turn can end in a curve that extends out of the plane of the balance spring and is shaped so that the balance spring's center of gravity remains substantially on the axis of the balance during oscillation of the regulating element, making the deformation of the balance spring concentric; hence, the balance spring is called a "Breguet balance spring." Other balance springs are not flat when at rest, but are cylindrical, conical, or spherical. A perfectly flat balance spring does not necessarily have to be shaped like an Archimedean spiral. A perfectly flat balance spring can have a variable pitch, a variable cross section, or one or more end curves to limit the displacement of the balance spring's center of gravity during oscillation of the governor member and to concentrically deform the balance spring.

[0003] An important characteristic of a regulating element is its quality factor, i.e., the ratio of energy stored to energy dissipated during a period of oscillation. A regulating element with a high quality factor requires less energy to maintain its oscillation at a given oscillation amplitude. One way to increase the quality factor is to reduce the friction of the staff pivot in the bearing. For example, certain materials with extremely low friction coefficients can be used for this purpose, or the geometry of the components can be modified to reduce the size of the contact surface. U.S. Pat. No. 3,186,157 describes another solution in which the balance is associated with two flat balance springs, one on each side of the balance, that not only perform an elastic return function but also have sufficient strength to reduce friction in the bearing by suspending the balance axially. However, this solution was specifically proposed for electric watches, where the regulating element's oscillations are rapid and small, and is disadvantageous for mechanical watches. In fact, in mechanical watches, the frequency is much lower and the amplitude of oscillation is much greater, so that to maintain a given frequency and amplitude, any strengthening of the balance spring (increase in dimensions or Young's modulus) must be compensated for by an increase in the inertia of the balance and by an increase in the force provided to maintain the oscillation, which is contrary to the objective sought.

[0004] In its opening paragraphs, U.S. Patent No. 3,186,157 mentions that the prior art has other solutions for reducing friction in the bearings, namely, solutions that consist of suspending the balance by means of a magnetic device or a spiral spring. The disadvantage of the magnetic device is that its components are sensitive to magnetic forces, which can disrupt the operation of the watch. Spiral springs are not mentioned. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 3,186,157 Summary of the Invention [Problem to be solved by the invention]

[0006] The invention aims to propose a device equipped with a regulating element whose quality factor is improved by mechanical solutions other than those consisting of increasing the force of the balance spring, and more precisely by mechanical solutions adapted to the vibration frequencies and amplitudes found in mechanical watches. [Means for solving the problem]

[0007] To this end, the subject of the present invention is a device with a regulating member for a timepiece, comprising a frame and a regulating member, the regulating member comprising a balance fixedly attached to a stack, and first and second balance springs, each of the first and second balance springs having an inner end fixedly attached to one of the staff and the frame and an outer end fixedly attached to the other of the staff and the frame, the staff having a pivot axis arranged to rotate in a bearing in the frame, the first and second balance springs being preloaded so as to exert two opposite forces on the staff parallel to the staff.

[0008] The present invention further proposes a timepiece, particularly a mechanical timepiece, equipped with such a speed regulating member.

[0009] Other features and advantages of the present invention will become apparent from the following detailed description, which is given in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view of a portion of a device with a regulating member according to the present invention; [Figure 2] 1 is a side view of a portion of a device with a regulating member according to the present invention. [Figure 3] 1 is a perspective view of a speed governor member of a device according to the invention; FIG. [Figure 4]FIG. 1 is a side view of a governor member of a device according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] 1 to 4, a device for a timepiece, in particular a timepiece such as a wristwatch, and more particularly a mechanical timepiece, comprising a regulating member 1 according to the invention, comprises a frame 2 and a regulating member 3 mounted on or in the frame 2. In the example shown, the frame 2 belongs to the movement of the timepiece and thus forms the fixed part of the timepiece. The frame 2 comprises a plate 4 which supports the moving components of the movement and has a through opening 5 in which the regulating member 3 is arranged. The frame 2 further comprises bridges fixed to the plate 4, in particular two balance cocks 6, 7, each in the form of a bar or arm, one fixed to the upper side of the plate 4 and the other fixed to the lower side, extending above and below the through opening 5, respectively.

[0012] The regulating member 3 comprises a balance 8 fixedly mounted on a staff 9 and two balance springs 10, 11 arranged on either side of the balance 8 and fixed by their inner ends to the staff 9 via respective collets 12, 13. The balance 8, staff 9 and balance springs 10, 11 share a common geometric axis A, which forms the axis of rotation of the balance 8-staff 9-collet 12, 13 assembly during operation. The ends of the staff 9, i.e., the staff pivots 14, 15, are arranged to rotate in respective bearings 16, 17 arranged in the two balance bridges 6, 7. In addition to the bearings 16, 17, each balance bridge 6, 7 has, in a conventional manner per se, a balance spring stud holder (only one of which, 18, is visible in the drawings) arranged to receive a balance spring stud 20, 21 to which the outer end of the corresponding balance spring 10, 11 is fixed. Each balance spring 10, 11 is thereby connected by its inner end to the staff 9 and by its outer end to the frame 2.

[0013] The staff 9 further has a fixedly mounted double balance roller 22 on which projects an impulse pin 23 intended to cooperate in the conventional way with an escapement anchor to maintain the oscillations of the balance 8.

[0014] In accordance with the present invention, the balance springs 10, 11 are axially preloaded by spaced apart positions of the inner and outer ends of each balance spring 10, 11 along axis A, such that two opposing forces parallel to axis A are exerted by the balance springs 10, 11 on the staff 9. In certain embodiments, the preload of each balance spring 10, 11 is achieved by moving its inner and outer ends away from each other along axis A a distance equal to or greater than one turn of the balance spring 10, 11, preferably equal to or greater than several turns of the balance spring 10, 11, relative to the balance spring's rest state. In some embodiments, the preload of each balance spring 10, 11 is achieved by spaced apart its inner and outer ends along axis A a distance equal to or greater than 0.1 mm, preferably equal to or greater than 0.2 mm, preferably equal to or greater than 0.5 mm, preferably equal to or greater than 1 mm, preferably equal to or greater than 1.5 mm, relative to the balance spring's rest state. Typically, as can be seen from the drawings, the balance springs 10, 11 each have a convex shape when coupled to the staff 9 and the frame 2, the two convex shapes being preferably portions of a sphere and preferably symmetrical to each other with respect to a plane perpendicular to the axis A.

[0015] Before being assembled with the staff 9 and frame 2, the balance springs 10, 11 can be completely flat balance springs, Breguet balance springs (flat balance springs with an end curve, or "Phillips curve," that moves out of the plane of the balance spring toward and back toward the axis of rotation, maintaining the balance spring's center of gravity on the axis of rotation), or other types. According to a particularly advantageous embodiment corresponding to that shown in the drawings, the balance springs 10, 11, before being assembled with the staff 9 and frame 2, are flat balance springs with a Phillips end curve, which differs from Breguet balance springs in that the lift of the Phillips curve out of the plane of the balance spring is achieved solely by elastic deformation of the balance spring, i.e., without any plastic deflection, as occurs with the Phillips curve of a cylindrical balance spring. Indeed, by axially separating the inner and outer ends of each balance spring 10, 11 after assembly with the staff 9 and frame 2, it is possible to avoid contact between the Phillips curve and the axial turns, despite the absence of any deflection that would lift the Phillips curve. Eliminating plastic deflection has the advantage that it does not adversely affect the mechanical properties of the balance spring, particularly its stiffness and elastic limit.

[0016] In the embodiment shown, balance spring 10 is stretched axially by preload, drawing staff 9 towards the upper balance cock 6, and balance spring 11 is stretched axially by preload, drawing staff 9 towards the lower balance cock 7. However, the opposite configuration is also possible, in which case the positions of the inner and outer ends of each balance spring 10, 11 along axis A are reversed; to this end, each balance cock 6, 7 could be provided with an arm extending to a point close to the balance wheel 8 and fixing the outer end of balance spring 10 to frame 2 at this point, with axial extension of balance spring 10 having the effect of drawing staff 9 towards the lower balance cock 7 and axial extension of balance spring 11 having the effect of drawing staff 9 towards the upper balance cock 6.

[0017] The two opposing forces acting on the staff 9 by the balance springs 10, 11 make it possible to at least partially suspend the staff 9 in the axial direction, thereby eliminating or reducing the axial support force of the pivots 14, 15 in the bearings 16, 17 and the resulting friction, due to the balance created between these two forces and the axial support force of the pivots 14, 15 in the bearings 16, 17. The greater the two opposing forces acting on the staff 9 by the balance springs 10, 11, the smaller the axial support force of the pivots 14, 15 in the bearings 16, 17. The two opposing forces can have the same magnitude, for example by being provided by the same balance springs 10, 11, but they can also have different magnitudes.

[0018] With respect to conventional balance springs, balance springs with one or more end curves, such as the balance springs 10 and 11 with Phillips curves shown in the drawings, Breguet balance springs, or completely flat balance springs of the type described in patents CH697207 and EP2138912, have the advantage of concentrically deforming and thus reducing the radial support force and resulting friction of the pivot shafts of the bearings, regardless of the angular orientation of the balance springs relative to one another. For this reason, these balance springs are preferred in the present invention. However, balance springs 10 and 11 could also be conventional balance springs without end curves that would concentrically deform these springs. In this case, however, they are preferably wound in opposite directions or angularly offset by 180° relative to one another so that the respective radial forces acting on staff 9 due to these eccentric deformations cancel each other out, thereby reducing the radial support force and resulting friction of pivot shafts 14 and 15 in bearings 16 and 17.

[0019] The invention has been described above by way of example only. It goes without saying that modifications are possible without departing from the scope of the claims. For example, instead of forming a fixed part of the timepiece, frame 2 could be a movable frame, such as the cage of a tourbillon or carousel, in which staff 9 and balance 8 are axially suspended by balance springs 10, 11. Another modification could consist in connecting the inner ends of balance springs 10, 11 to frame 2 instead of staff 9, and connecting the outer ends of balance springs 10, 11 to balance 8 instead of frame 2. Finally, although for layout reasons balance springs 10, 11 are preferably located on either side of balance 8, they could also be located on the same side of balance 8, as long as they directly or indirectly exert two opposing forces on staff 9 parallel to staff 9.

Claims

1. A device with a regulating member for a timepiece, comprising a frame (2) and a regulating member (3), said regulating member (3) comprising a balance (8) fixedly attached to a staff (9) and first and second balance springs (10, 11), each of said first and second balance springs (10, 11) having an inner end fixedly attached to one of said staff (9) and said frame (2) and an outer end fixedly attached to the other of said staff (9) and said frame (2), said staff (9) having a pivot (14, 15) arranged to rotate in bearings (16, 17) of said frame (2), 10. A device according to claim 9, characterized in that said first and second balance springs (10, 11) are preloaded to exert two opposite forces on said staff (9) parallel to said staff (9).

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

3. 3. A device according to claim 1 or 2, characterized in that the inner end of each of the first and second balance springs (10, 11) is fixedly attached to the staff (9) and the outer end of each of the first and second balance springs (10, 11) is fixedly attached to the frame (2).

4. A device according to any one of claims 1 to 3, characterized in that each of the first and second preloaded balance springs (10, 11) has a convex shape.

5. 5. A device according to claim 4, characterized in that the convex shape of each of the first and second preloaded balance springs (10, 11) is in the shape of a portion of a sphere.

6. 6. A device according to claim 4 or 5, characterized in that the convex shape of the first balance spring (10) and the convex shape of the second balance spring (11) are symmetrical with respect to a plane perpendicular to the staff (9).

7. 7. A device according to any one of claims 1 to 6, characterized in that each of the first and second balance springs (10, 11) is a balance spring with concentric deformation.

8. 8. A device according to any one of claims 1 to 7, characterized in that each of the first and second balance springs (10, 11) is a flat balance spring with a Phillips curve in which the preload gives it a convex shape.

9. 9. The device of claim 8, wherein each of the first and second balance springs (10, 11) has no plastic deflection between the Phillips curve and the rest of the balance spring.

10. 7. A device according to any one of claims 1 to 6, characterized in that the first and second balance springs (10, 11) are wound in opposite directions or offset by 180° so that the respective radial forces that the balance springs (10, 11) exert on the staff (9) as a result of eccentric deformation of the balance springs (10, 11) during oscillation of the governor member (3) cancel each other.

11. A device according to any one of claims 1 to 10, characterized in that the device consists of a clock movement.

12. 11. The device according to any one of claims 1 to 10, characterized in that the device consists of a tourbillon or a carousel.

13. A watch comprising a device according to any one of claims 1 to 12.

14. A mechanical watch comprising a device according to any one of claims 1 to 12.

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