BALANCE WHEEL-SPRING ASSEMBLY OF TIMEPIECE

Abstract

A balance wheel-spring system including a balance wheel that oscillates about a balance wheel shaft and a spring, one inner spiral of which is fixed to the balance wheel shaft or to a collet mounted integrally with the shaft and one outer spiral of which is fixed to a stud integral with a bridge. The balance wheel includes a hub, a rim, an arm connecting the hub to the rim, a front face which includes a countersink and a rear face, the arm including a housing receiving and retaining a flyweight, and the spring being mounted opposite the front face of the balance wheel. The flyweight is mounted on the arm on the rear face of the balance wheel, the distance between the bottom of the countersink of the front face of the balance wheel and the spring is a predetermined interval between 0.05 mm and 1.50 mm.

Claims

1-9. (canceled)

10: A balance wheel-spring system comprising: at least one balance wheel which oscillates about a pivot axis via a balance wheel shaft mounted between a bottom plate and a bridge and aligned on the pivot axis; and at least one spring, one inner spiral of which is fixed to the balance wheel shaft or to a collet mounted integrally with the balance wheel shaft and one outer spiral of which is fixed to a stud integral with the bridge bearing the balance wheel shaft; the balance wheel comprising a balance wheel hub, a rim, at least one arm connecting the hub to the rim, a front face of which includes a countersink and a rear face, the at least one arm comprising a housing for receiving and retaining at least one flyweight comprising a head and a rod, and the spring being mounted opposite the front face of the balance wheel, wherein the at least one flyweight is mounted on the rear face of the balance wheel, on the at least one arm of the balance wheel, wherein the head resting against the rear face of the balance wheel and the rod is flush with the bottom of the countersink, and wherein the distance between the bottom of the countersink of the front face of the balance wheel and the spring is at a predetermined interval between 0.05 mm and 1.50 mm.

11: A system according to claim 10, wherein the predetermined interval is between 0.10 mm and 0.70 mm.

12: A system according to claim 10, wherein the rod rests in the housing.

13: A system according to claim 10, wherein the head of the at least one flyweight comprises control means to adjust the at least one flyweight from the rear face of the balance wheel.

14: A system according to claim 10, wherein the diameter of the rod of the at least one flyweight is at least equal to the width of the housing.

15: A system according to claim 10, wherein the at least one arm, the rim, and the hub form a monobloc element.

16: A timepiece movement comprising a balance wheel-spring system according to claim 10.

17: A timepiece comprising a movement according to claim 16.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Other features and advantages of the invention will appear more clearly upon reading the following description of one particular embodiment of the invention, given by way of simple example which is illustrative and non-limiting, and of the annexed Figures, amongst which:

[0021] FIG. 1a is a view from below of a balance wheel according to the invention;

[0022] FIG. 1b is a sectional view according to the line A-A of FIG. 1 of a balance wheel according to the invention;

[0023] FIG. 2 is a sectional view according to the line A-A of FIG. 1 of a balance wheel-spring system according to the invention, which equips a timepiece movement.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0024] A balance wheel-spring assembly according to one embodiment will now be described in the following with reference jointly to FIGS. 1a, 1b and 2.

[0025] The invention thus relates to a timepiece balance wheel-spring system, which is intended to be incorporated in an oscillating mechanism in the centre of a timepiece movement, and comprising at least one balance wheel 1 which oscillates about a pivot axis P via a balance wheel shaft 40 aligned on the axis P and at least one spring 2.

[0026] As can be seen in FIG. 2, the balance wheel shaft 40 is mounted between a bottom plate 13 and a bridge 9, the balance wheel shaft 40 having, at each of its ends, a conical pivot 41 for allowing the balance wheel shaft 40 to pivot about the pivot axis P while limiting friction. An inner spiral (not visible in the Figures) of the spring 2 is fixed to the balance wheel shaft 40 or to a collet 7 which can be monobloc with the spring 2 which is mounted integrally with the balance wheel shaft 40 and an outer spiral 21 of the spring 2 is fixed to a stud 8 which is integral with a bridge 9.

[0027] The invention is described here in the particular case of a single balance wheel and single spring adjusting element, the person skilled in the art will be able to extrapolate the invention to the cases of a plurality of balance wheels and/or a plurality of springs.

[0028] As can be seen in the Figures, the balance wheel 1 comprises a hub 3 which bears the balance wheel shaft 40, a rim 4, at least one arm 5 connecting the hub 3 to the rim 4, a front face 10 which has a countersink 11 and a planar rear face 12 which can also be countersunk. The arm 5 comprises a housing 6 for receiving and retaining at least one flyweight 30, and the spring 2 is mounted opposite the front face 10 of the balance wheel 1 which receives the countersink 11.

[0029] As can be seen in FIGS. 1a and 1b, the balance wheel 1 comprises rigid parts formed by the hub 3, the rim 4, and the arm 5 connecting the rim 4 to the hub 2. The housing 6 is delimited, on one hand by a rigid part of the balance wheel 1, and on the other hand by an elastically deformable portion 61.

[0030] The arm 5 comprises a housing 6 for receiving and clamping in position a rod 32 of a flyweight 30. This flyweight 30 comprises a head 31 which has control means, such as an adjustment profile 33 provided for cooperating with a tool, such as a screwdriver. Thus, the flyweight 30 can be adjusted from said rear face 12 of the balance wheel 1. The rod 32 of the flyweight 30 extends the head 31, which is of a greater diameter than that of the rod 32.

[0031] The diameter of the rod 32 of the flyweight 30 is chosen to be of a greater width than the housing 6 so that the rod 32 is retained by the elastically deformable portion 61, the portion 61 exerting a restoring force.

[0032] Advantageously, the length of the rod 32 does not exceed the thickness of the arm 5 such that the rod 32 does not project and thus optimises the arrangement of the parts in the centre of the movement in order to gain in compactness.

[0033] This simple configuration of a flyweight 30 formed solely by the head 31 and the rod 32 is favourable for assembly of the flyweight on the balance wheel 1 from the bottom of the latter.

[0034] The flyweight 30, once clamped in the housing 6, can be orientated angularly via the bias of a tool without being impeded by the spring 2 or by the little available space. The flyweight 30 comprises an unbalance produced by means of a flattened portion 34 provided on the head 31, as can be seen in FIG. 1a, in order to allow adjustment of the inertia of the balance wheel 1.

[0035] According to the invention, the flyweight 30 is mounted on the side of the rear face 12 of the balance wheel 1, the head 31 resting against the rear face 12 of the balance wheel 1 below the arm 5, the distance between the bottom of the countersink of the front face 10 of the balance wheel 1 and the spring 2 is at a predetermined interval V between 0.05 mm and 1.50 mm. In a more preferred manner, the predetermined interval V is between 0.10 mm and 0.70 mm. Such an arrangement makes it possible to obtain a compact arrangement and thus to reduce the bulkiness of the timepiece movement.

[0036] Particularly advantageously, the rod 32 is flush with the bottom of the countersink 11 of the front face 10 of the balance wheel 1 such that the countersink 11 has no projecting element, the stud 8 therefore being able to be provided nearest the rim 4, the stud 8 even being able to be situated nearest the bottom of the countersink 11.

[0037] The arm 5, the rim 4 and the hub 3 form the same monobloc element, the balance wheel 1 being able to be produced in a metallic material.

[0038] The invention likewise relates to a timepiece movement and a timepiece which are equipped with a balance wheel-spring system according to the invention.

[0039] Thanks to these various aspects of the invention, a compact balance wheel-spring system is available, which makes it possible to reduce the thickness of the timepiece movement and implicitly the thickness of the watch case so as to provide a relatively slim watch.

[0040] Of course, the present invention is not limited to the illustrated example and can have various variants and modifications which will be apparent to the person skilled in the art.

PARTS LIST

[0041] 1. Balance wheel [0042] 2. Spring [0043] 21. Outer spiral [0044] 3. Hub [0045] 4. Rim [0046] 5. Arm [0047] 6. Housing [0048] 61. Elastic portion [0049] 7. Collet [0050] 8. Stud [0051] 9. Bridge [0052] 10. Front face [0053] 11. Countersink [0054] 12. Rear face [0055] 13. Bottom plate [0056] 30. Flyweight [0057] 31. Head [0058] 32. Rod [0059] 33. Adjustment profile [0060] 34. Flattened portion [0061] 40. Balance wheel shaft [0062] 41 Pivot [0063] P. Pivot axis [0064] V. Predetermined value