Timepiece staff

Abstract

The invention relates to a timepiece staff (1), in particular a staff for a balance (2) or a staff for an escape wheel or a staff for an anchor, the staff comprising: - a first axis of rotation (A1); and - at least one pivot (12), the timepiece staff (1) having a surface of revolution about the first axis of rotation (A1), of which the generatrix (G), in a plane (P) passing through the first axis of rotation (A1), is curved, this surface of revolution extending at least at the pivot, the pivot being defined as the region of the timepiece staff (1) that is intended to come into contact with a pivot bearing (50), in particular with a pivot jewel (50).

Description

[0001] Watchmaking axis.

[0002] The invention relates to a watch axis. The invention also relates to an element intended to be attached to a watch axis. The invention also relates to an assembly comprising such an axis and / or such an element. The invention further relates to an assembly comprising such an axis or such an element or such an assembly. The invention further relates to a watch movement comprising such an axis or such an element or such an assembly or such an assembly. The invention finally relates to a timepiece comprising such an axis or such an element or such an assembly or such a watch movement.

[0003] Numerous studies and patent applications aim to identify a material and / or geometry for movement axes that are both paramagnetic and resistant to mechanical stresses when worn. This research focuses in particular on balance axes, which are particularly stressed. Historically, watch axes have been made of carbon steel, which is ferromagnetic. The paramagnetic alloys tested so far are significantly less efficient from a mechanical point of view. The mechanical resistance of watch axes therefore remains a problem.

[0004] Document WO2021032552A1 describes a particular drilling geometry for a pivot stone. A pivot is schematically described in Figure 2 with a truncated cone geometry, without further details.

[0005] Document CH702314 describes a specific pivot geometry, with a conical pivot that cooperates with a counter-pivot jewel surface in the shape of an inverted pyramid. Document CH704770 describes different geometries of the end of a pivot that cooperates with a counter-pivot jewel. In the vertical position of the movement, a portion of the cylindrical surface of the pivot is in contact with the internal surface of the bearing. In the horizontal position of the movement, the end of the pivot is in contact with the counter-pivot jewel. Document CH704770 is particularly interested in the geometry of the end, by proposing to misalign the point of support of the watch axis on the counter-pivot jewel from the pivot axis.

[0006] Document EP3258325 discloses a ceramic balance staff. The kingpin and the pivot may be the same or not be delimited by a clear boundary such as a bearing surface. The kingpin and the pivot may, for example, be separated by a truncated cone-shaped surface or a surface with a curved generatrix. The staff comprises a standard geometry at its middle part, with receiving portions for a roller (cylindrical portion), a balance with a receiving plate forming a stop and a cylindrical portion and a collet (not shown).

[0007] The NIHS-34-01 standard describes standard geometries of balance shafts. The shaft comprises several portions, including cylindrical portions, bearing surfaces perpendicular to the axis of symmetry forming stops, and frustoconical portions. These frustoconical portions are not, however, bearing or stop surfaces, but entry chamfer surfaces to facilitate the assembly of components attached to the shaft and / or machining. In particular, the plate and the balance are driven in, bearing on the flat or substantially flat surfaces of the plate. The pivots are described as being cylindrical in shape with a diameter p, which extend into a cone or a surface of revolution evolving into an arc of a circle with a radius r. A. Haag, in “Theoretische und experimentelle Untersuchungen zum Verhalten der Unruhzapfen bei Stoessen auf die Uhr” (Proceedings of the International Congress of Chronometry 1964, p.1 125), describes a general plan of a balance shaft, with flat bearing or stop surfaces and conical receiving portions, which form a fitting cone. This type of cone is used because it ensures very good centering and easy assembly. The fitting cone (sometimes called Morse taper) is based on the fitting of two male and female elements whose conical walls typically have conicity angles of a few degrees, and is used to fix parts together in fields such as the machine tool industry and dental applications.

[0008] Document CH327357 describes a shaft geometry designed to facilitate the disassembly of the various elements. The shaft comprises a cylindrical receiving portion, with optionally a low-angle conical portion and / or a shoulder. The various elements are driven out with corresponding bores on the cylindrical portions.

[0009] Document CH715867 describes an axis geometry comprising several straight truncated cone sections. These parts are intended to facilitate the driving of the various elements added onto the axis (hairspring collet, balance wheel, plate) and / or the machining of the axis, but do not constitute support or stop surfaces for the added elements. On the contrary, the collet and the plate rest on flat surfaces forming shoulders, i.e. forming flat bearing surfaces perpendicular to the axis of revolution of the axis.

[0010] Document FR2268291 describes an optimized balance staff geometry for making the staff from drawn wires, without a surface for holding, supporting, or stopping the balance or the roller. The Illustrated Professional Dictionary of Watchmaking (G. -A. Berner) indicates that one type of pivot is incorrectly called "conical." It should rather be called a pivot without a bearing. It is formed by a cylindrical part connected by a fillet to the tigeron. It is part of a watch staff pressing by its end against the face of a counter-pivot jewel. Since the bearing is removed, friction is reduced.

[0011] C. Schlatter and H. -A. Lehmann, in “Measurements of the fragility of balance shaft pivots” (proceedings of the 46 eCongress of the Swiss Society of Chronometry, p. 157, 1971) measure the bending resistance of different pivot geometries. A continuous connection between the cylindrical part (the pivot) and the conical part is recommended. In addition, tests with "rounded cone" geometries (fillet) are more favorable than actual cone geometries for connecting the cylindrical portion of the pivot to the tang.

[0012] The aim of the invention is to provide a watch axis which overcomes the problems mentioned above and makes it possible to improve the watch axes known from the prior art. In particular, the invention proposes a watch axis whose mechanical resistance is improved.

[0013] According to a first aspect of the invention, objects are defined by the following propositions.

[0014] 1. Watch axle 1, in particular axle for balance wheel 2 or axle for escape wheel or axle for anchor, comprising:

[0015] - a first axis of rotation A1, and

[0016] - at least one pivot 12, the watch axis 1 having a surface of revolution around the first axis of rotation A1, the generator G of which, in a plane P passing through the first axis of rotation A1, is curved, this surface of revolution extending at least at the level of the pivot, the pivot being defined as the zone of the watch axis 1 intended to come into contact with a pivot bearing 50, in particular with a pivot jewel 50. Watch axis 1 according to proposition 1, characterized:

[0017] - in that the generator G comprises at all points a radius of curvature less than 2 mm, in particular less than 1.8 mm, and / or

[0018] - in that the diameter of the cross-section of the surface of revolution increases continuously as one moves away from the proximal end 13 of the clock axis 1, and / or

[0019] - in that the generator G has a radius of curvature which decreases as one moves away from the proximal end 13 of the watch axis 1. Watch axis 1 according to one of propositions 1 and 2, characterized in that the generator G has, at the pivot, a first portion 121 seen convex from the first axis of rotation A1. Watch axis 1 according to one of propositions 1 to 2, characterized in that the generator G has, at the pivot, a first portion 121 seen concave from the first axis of rotation A1. Watch axis 1 according to proposition 4, characterized in that the distance R from the first portion to the first axis of rotation A1 increases according to the following law as a function of the distance d to the proximal end 13 of the watch axis 1: R = A x (d+B) 1 / 3, with A and B constant numbers. Watch axis 1 according to proposition 3 or 4, characterized in that the first portion 121 is a portion of a circle having a first radius of curvature R1. Watch axis 1 according to one of propositions 3 to 6, characterized in that the generator G has a second portion seen convex 122 from the first axis of rotation A1, the first and second portions being connected continuously, in particular continuously in tangency and / or continuously in curvature. Watch axis 1 according to proposition 7, characterized in that the second portion 122 is a portion of a circle having a second radius of curvature R2. Clock axis 1 according to one of proposals 1 to 8, characterized in that the generator G consists of a spline curve, or of portions of spline curves connected continuously, in particular continuously in tangency and / or continuously in curvature.Watch axis 1 according to one of the propositions 1 to 9, characterized in that the watch axis has several surfaces of revolution and in that the surfaces of revolution of the watch axis 1 around the first axis of rotation A1 each have a generator which, in a plane P passing through the first axis of rotation A1, has a radius of curvature greater than 40 pm or 50 pm at any point of the generator. Watch axis 1 according to one of the propositions 1 to 10, characterized in that the watch axis 1 is made of: - a technical ceramic, in particular zirconia or alumina, or.

[0020] - a glass, in particular a metallic glass, or

[0021] - a steel, in particular a carbon steel, or

[0022] - a paramagnetic austenitic steel, or

[0023] - a metal alloy, or

[0024] - a high entropy alloy, or

[0025] - a composite material, in particular a composite material comprising a ceramic filler in a metal matrix. Assembly 150, in particular assembled balance wheel 150, comprising a watch shaft 1 according to one of proposals 1 to 11. Assembly 100 comprising:

[0026] - a clockwork axis 1 according to one of proposals 1 to 11 or an assembly 150 according to proposal 12, and

[0027] - a pivot bearing 50, in particular a pivot stone 50. Assembly 100 according to proposal 13, characterized in that the pivot bearing 50 includes a pivot stone 50 comprising a hole 51 along a second axis of rotation A2 for the pivoting of the watch axis 1, the hole comprising:

[0028] - a first pivoting zone 52 of the clock axis 1, and

[0029] - a second clearance zone 53 extending from a first face 54 of the bearing to the first pivot zone 52, the face 54 being perpendicular or substantially perpendicular to the second axis of rotation A2 and intended to be oriented towards the body of the watch axis 1, the first pivot zone 52 and the second clearance zone 53 connecting to each other by a connecting rounded portion 55. 15. Assembly 100 according to proposal 14, characterized in that the second clearance zone 53 comprises a maximum diameter greater than twice or greater than four times or greater than six times the minimum diameter of the first pivot zone 52.

[0030] 16. Watch movement 200 comprising a watch axis 1 according to one of the propositions 1 to 11 and / or an assembly according to proposition 12 and / or an assembly according to one of the propositions 13 to 15.

[0031] 17. Timepiece 300, in particular wristwatch, comprising a watch movement 200 according to proposition 16 and / or a watch axis 1 according to one of propositions 1 to 11 and / or an assembly according to proposition 12 and / or an assembly according to one of propositions 13 to 15.

[0032] According to a second aspect of the invention, objects are defined by the following propositions.

[0033] 18. Watch axis 1 comprising a first portion 24 for driving an element 2; 3; 4 along a driving axis A1, the watch axis 1 having a geometry: having a first frustoconical stop portion 21 arranged to stop an element 2; 3; 4 during its driving onto the watch axis 1, the first stop portion 21 having a half-angle at the apex of between 30° and 60°, and such that the distance L measured along the driving axis A1 and separating the first driving portion 24 from the first stop portion 21 is at least 0.05 mm, or even at least 0.1 mm. Watch shaft 1 according to proposition 18, characterized in that the watch shaft is a balance shaft 2. Watch shaft 1 according to one of propositions 18 and 19, characterized in that the first driving portion 24 and the first stopping portion 21 are separated by a separation portion 25 having a diameter smaller than that of the first driving portion 24.Watch axis 1 according to proposal 20, characterized in that the first driving portion 24 and the separation portion 25 are connected by one or more fillets and / or in that the first stopping portion 21 and the separation portion 25 are connected by one or more fillets. Watch axis 1 according to one of proposals 18 to 21, characterized in that the axis is made of:.

[0034] - a technical ceramic, in particular zirconia or alumina, or

[0035] - a glass, in particular a metallic glass, or

[0036] - a steel, in particular a carbon steel, or

[0037] - a paramagnetic austenitic steel, or

[0038] - a metal alloy, or

[0039] - a high entropy alloy, or

[0040] - a composite material, in particular a composite material comprising a ceramic filler in a metal matrix. Watch shaft 1 according to one of the proposals 18 to 22, characterized in that the watch shaft 1 has a geometry of revolution around the driving axis A1. Watch shaft 1 according to one of the proposals 18 to 23, characterized in that the watch shaft 1 has surfaces of revolution around the driving axis A1 and in that the surfaces of revolution each have a generatrix which, in a plane P passing through the driving axis A1, has a radius of curvature greater than 40 pm or 50 pm at any point of the generatrix. Watch shaft 1 according to one of the proposals 18 to 24, characterized in that the watch shaft 1 comprises at least one pivot 12, preferably two pivots. Element 2; 3; 4 intended to be driven onto a watch axis 1 along a driving axis A1, the element 2; 3; 4 comprising:

[0041] - a second portion 34 of chasing on a clock axis 1, and

[0042] - a second truncated cone-shaped stop portion 31 arranged to stop the element 2; 3; 4 when it is driven onto a watch axis 1, the second stop portion having a half-angle at the apex of between 30° and 60°, the distance L measured along the driving axis A1 between the second driving portion 34 and the second stop portion 31 being at least 0.05 mm, or even at least 0.1 mm. Element 2; 3; 4 according to proposition 26, characterized in that the element 2; 3; 4 is a balance wheel 2 or a plate or a double plate 3 or a collet 4. Element 2; 3; 4 according to proposition 26 or 27, characterized in that the element 2; 3; 4 comprises a recess 35 between the second driving portion 34 and the second stopping portion 31. 29. Assembly 150, in particular assembled balance 150, comprising:

[0043] - a watch axis 1, in particular a watch axis 1 according to one of proposals 18 to 25, and

[0044] - an element 2; 3; 4 driven onto the clock axis 1, in particular an element 2; 3; 4 according to one of the propositions 26 to 28.

[0045] 30. 200 watch movement including:

[0046] - a clock axis 1 according to one of the proposals 18 to 25, and / or

[0047] - an element 2; 3; 4 according to one of propositions 26 to 28, and / or

[0048] - an assembly according to proposition 29.

[0049] 31. Timepiece 300, in particular wristwatch, comprising:

[0050] - a 200 clock movement according to proposition 30, and / or

[0051] - a clock axis 1 according to one of the proposals 18 to 25, and / or

[0052] - an element 2; 3; 4 according to one of propositions 26 to 28, and / or

[0053] - an assembly 150 according to proposition 29.

[0054] According to a third aspect of the invention, objects are defined by the following propositions.

[0055] 32. Assembly 150, in particular assembled balance wheel 150, comprising:

[0056] - a clock axis 1, and

[0057] - an element 2; 3; 4 driven onto the watch axis 1, the watch axis 1 having a first driving portion 24 and a first stop portion 21 arranged to stop the element 2; 3; 4 when it is driven onto the watch axis 1, the element 2; 3; 4 having a second driving portion 34 onto the watch axis 1 and a second stop portion 31 arranged to stop the element 2; 3; 4 when it is driven onto the watch axis 1, the first driving portion 24 and the first stop portion 21 being separated by a separation portion 25 having a diameter smaller than that of the first driving portion 24, and / or the element 2; 3; 4 comprising a recess 35 between the second driving portion 34 and the second stopping portion 31.Assembly 150 according to proposition 32, characterized in that the first stop portion 21 is frustoconical and has, for example, a half-angle at the apex of between 30° and 60° and / or in that the distance L measured along the driving axis A1 and separating the first driving portion 24 from the first stop portion 21 is at least 0.05 mm, or even at least 0.1 mm. Assembly 150 according to proposition 32 or 33, characterized in that the watch shaft is a balance shaft 2. Assembly 150 according to one of propositions 32 to 34, characterized in that the first driving portion 24 and the separation portion 25 are connected by one or more fillets and / or in that the first stop portion 21 and the separation portion 25 are connected by one or more fillets. Assembly 150 according to one of the proposals 32 to 35, characterized in that the clock axis 1 is made of:.

[0058] - a technical ceramic, in particular zirconia or alumina, or

[0059] - a glass, in particular a metallic glass, or

[0060] - a steel, in particular a carbon steel, or

[0061] - a paramagnetic austenitic steel, or

[0062] - a metal alloy, or

[0063] - a high entropy alloy, or

[0064] - a composite material, in particular a composite material comprising a ceramic filler in a metal matrix. Assembly 150 according to one of proposals 32 to 36, characterized in that the watch axis 1 has a geometry of revolution around the driving axis A1. Assembly 150 according to one of proposals 32 to 37, characterized in that the watch axis 1 has surfaces of revolution around the driving axis A1 and in that the surfaces of revolution each have a generatrix which, in a plane P passing through the driving axis A1, has a radius of curvature greater than 40 pm or 50 pm at any point of the generatrix. Assembly 150 according to one of proposals 32 to 38, characterized in that the watch axis 1 comprises at least one pivot 12, preferably two pivots.Assembly 150 according to one of the proposals 32 to 39, characterized in that the second stop portion is frustoconical and has a half-angle at the apex of between 30° and 60° and / or in that the distance L measured along the driving axis A1 between the second driving portion 34 and the second stop portion 31 is at least 0.05 mm, or even at least 0.1 mm. Assembly 150 according to one of the proposals 32 to 40, characterized in that the element 2; 3; 4 is a balance wheel 2 or a plate or a double plate 3 or a collet 4. Watch movement 200 comprising an assembly according to one of the proposals 32 to 41. 43. Timepiece 300, in particular a wristwatch, comprising:.

[0065] - a 200 clock movement according to proposition 42, and / or

[0066] - an assembly 150 according to one of the proposals 32 to 41.

[0067] Unless there is a logical or technical incompatibility, any combination of the characteristics of the first, second and third aspects is considered.

[0068] The attached drawings represent, by way of examples, two embodiments of a timepiece according to the invention.

[0069] Figure 1 is a schematic view of a first embodiment of a timepiece according to the invention.

[0070] Figure 2 is a partial sectional view of the first embodiment at a pivot.

[0071] Figure 3 is a partial sectional view of the first embodiment at the level of the assembly of a double-plate on a watch axis.

[0072] Figure 4 is a partial sectional view of a detail of a second embodiment of a timepiece according to the invention at the level of the assembly of a double-plate on a watch axis.

[0073] A first embodiment of a timepiece 300 is described below in detail with reference to Figures 1 to 3.

[0074] The timepiece 300 is for example a watch, in particular a wristwatch. The timepiece 300 comprises a watch movement 200 intended to be mounted in a timepiece case or box in order to protect it from the external environment.

[0075] The 200 watch movement can be a mechanical movement, especially an automatic movement, or a hybrid movement. Alternatively, the movement can be an electronic movement.

[0076] The 200 watch movement includes a 150 assembly including:

[0077] - a clock axis 1, and

[0078] - an element 2; 3; 4 mounted, in particular driven, on the clock axis 1.

[0079] The 200 watch movement includes a 100 set including:

[0080] - the clock axis 1 or the assembly 150, and

[0081] - a pivot bearing 50, in particular a pivot stone 50.

[0082] The pivot bearing 50 may include the pivot stone 50 and a counter-pivot stone 59. These pivot stones 50 and counter-pivot stones 59 may be part of a shock absorber system.

[0083] Preferably, the pivoting stone 50 comprises a hole 51 along a second axis of rotation A2 for the pivoting of the watch axis 1. The hole 51 advantageously comprises:

[0084] - a first pivoting zone 52 of the clock axis 1, and

[0085] - a second clearance zone 53 extending from a first face 54 of the bearing, in particular of the pivoting stone 50, to the first pivoting zone 52, the face 54 being perpendicular or substantially perpendicular to the second axis of rotation A2 and intended to be oriented on the side of a body 15 of the watch axis 1, the first pivoting zone 52 and the second clearance zone 53 connecting to each other by a connecting rounded part 55.

[0086] Preferably, the first pivot zone 52 is configured so as to have a minimum diameter distant from the two ends of the hole, in particular from the face 54 and from another face of the stone 50 opposite the face 54. In other words, the support zone of the watch axis 1 on the pivot stone 50 is not located on an edge of the hole 51. Preferably, the counter-pivot stone 59 comprises a flat contact surface intended to cooperate with the end 13 of the watch axis 1.

[0087] The use of such a pivot stone provided with such a clearance zone 53 makes it possible to improve performance by minimizing the pivot play and the risk of jamming of the watch axis 1 in the pivot stones 50 when using a watch axis 1 with optimized pivot geometry as described below. Indeed, surprisingly, the clearance zone 53 makes it possible to minimize the risk of jamming of a watch axis 1 whose diameter increases (along its geometric axis A1) more significantly than for a watch axis of standard geometry.

[0088] Advantageously, the second clearance zone 53 comprises a maximum diameter greater than two times or greater than four times or greater than six times the minimum diameter of the first pivot zone 52.

[0089] The assembly can be:

[0090] - an assembled balance wheel comprising a balance shaft, or

[0091] - an assembled escape wheel comprising an escape wheel axle, or

[0092] - an assembled escapement wheel comprising an escapement wheel shaft, or

[0093] - an assembled anchor comprising an anchor pin, or

[0094] - an assembled anchor mobile comprising an anchor mobile axis.

[0095] In the case of an assembled balance wheel, the element(s) may be:

[0096] - a balance 2, and / or

[0097] - a 3-tray, in particular a double-tray, and / or

[0098] - a ferrule 4, in particular a ferrule for a spiral spring.

[0099] According to the first aspect of the invention, the clockwork axis 1 preferably comprises:

[0100] - a first axis of rotation A1, and

[0101] - at least one pivot 12, the watch axis 1 having a surface of revolution around the first axis of rotation A1, the generator G of which, in a plane P passing through the first axis of rotation A1, is curved. This surface of revolution extends at least at the level of the pivot, the pivot being defined as the zone of the watch axis 1 intended to come into contact with a pivot stone 50.

[0102] Alternatively or additionally, in accordance with the second aspect of the invention, the watch axis 1 comprises a first portion 24 for driving an element 2; 3; 4 along a driving axis A1, the watch axis 1 having a geometry: having a first frustoconical stop portion 21 arranged to stop an element 2; 3; 4 when it is driven onto the watch axis 1, the first stop portion 21 having a half-angle at the apex (apex of the cone extending the truncated surface) of between 30° and 60°, and such that the distance L measured along the driving axis A1 between the first driving portion 24 and the first stop portion 21, i.e. separating the first driving portion 24 from the first stop portion 21, is at least 0.05 mm, or even at least 0.1 mm.

[0103] The first embodiment shown in Figures 1 to 3 combines these two aspects of the invention.

[0104] Preferably, the first axis of rotation A1 and the driving axis A1 coincide. For this reason, the two axes have been shown merged and bearing the same reference A1. Furthermore, apart from functional clearances, the first axis of rotation A1 and the second axis of rotation A2 also coincide.

[0105] Advantageously, the axis 1 comprises, at each of its ends, a pivot 12. More preferably, each pivot 12 is connected to the body 15 by means of a tigeron 14.

[0106] In the case of a balance staff, the staff performs different functions. On the one hand, the pivots 12 placed at the ends of the staff ensure the pivoting of a balance-spring assembly in cooperation with the bearings. To ensure good performance over time, this function requires:

[0107] - high mechanical resistance,

[0108] - a very careful surface condition in terms of roughness, and

[0109] - a very small diameter.

[0110] On the other hand, axis 1 carries constituent elements of the balance spring, such as:

[0111] - the balance wheel which forms a flywheel of given inertia,

[0112] - the balance spring which exerts a restoring torque on the oscillating assembly,

[0113] - the collet driven or assembled on axis 1 and which fixes the balance spring, or

[0114] - the single or double plate, which interacts for example with an escapement anchor by means of a pin to on the one hand unlock the escapement and on the other hand receive an impulse to maintain the oscillations of the sprung balance. The plate is said to be double when it comprises, in addition to the plate carrying the pin, an additional stage, generally of smaller diameter, equipped with a cutout which interacts with a pin of the anchor to form an anti-overturning system which prevents the inopportune unlocking of the escapement.

[0115] For example, each end 13 of the watch axis 1, in particular provided to come into contact against a counter-pivot stone 59, is not part of a pivot 12. Such a counter-pivot stone 59 is provided to delimit the longitudinal play of the watch axis 1, and not to allow the latter to pivot. The counter-pivot stone 59 therefore does not constitute a pivot stone.

[0116] Each end 13 of the clock axis 1 can be:

[0117] - convex and rounded, or

[0118] - flat, or

[0119] - concave, to come into contact with the counter-pivot stone 59.

[0120] For example, from the point on the surface of the clockwork axis having the most extreme abscissa relative to the axis A1, that is to say from the extreme point of the clockwork axis 1, the limit between the end 13 and the pivot 12 is located at the places where the plane tangent to the surface of the clockwork axis 1 forms an angle of less than 10° with the axis A1.

[0121] For example, the boundary between a connection zone and a pivot 12 is formed by a plane 150 pm or 210 pm or 250 pm away from the end of the axis. When moving on the surface of the watch axis from an extreme point (one end) of the watch axis 1 to another extreme point of the watch axis (another end), we successively encounter:

[0122] - one end 13,

[0123] - a pivot 12,

[0124] - a connecting zone connecting the pivot to a tigeron, and

[0125] - a tigeron 14.

[0126] The connecting zone comprises a portion of the surface of revolution (obtained by revolution of a portion 122 of the generating curve G).

[0127] The inventors' work shows, surprisingly, that the shape of the pivots must be rethought due to the nature of the material used. The rules derived from experience and empirical developments on high-hardness metal alloys do not necessarily apply to an axis made of high-performance technical ceramic, such as a yttria-containing zirconia axis of type 2YZ or 3YZ. This approach applies to the shape of the pivots, but also to the geometry of the central part 15 (or body 15) of the axis 1 on which the various elements attached to the balance wheel are assembled.

[0128] It was thus found that the traditional geometry of pivots worsens their mechanical resistance when a ceramic-type material is used. On the one hand, it is necessary to have a profile evolution that is as continuous as possible, avoiding any edge or abrupt change in dimension. Indeed, the simulations carried out highlight that each corner and / or edge and / or abrupt change in dimension induces a concentration of stresses, which should be avoided.

[0129] Redefining the transitions between the different parts or zones of the axis, in particular by avoiding the bearing surfaces perpendicular to the axis of rotation A1 and the edges, makes it possible to improve shock resistance and limit breakage. This is a break with the traditional shapes seen in the illustrations of the illustrated professional dictionary of watchmaking (G. -A. Berner), or even in application EP3594757 which nevertheless concerns an axis made of injectable material, such as ceramic. From a dimensional point of view, the inventors' work shows that it is appropriate to adapt the radii of curvature in the connection zones to minimize stresses, in particular to have radii greater than 40 pm, or even ideally greater than 50 pm.This first adjustment of the connection radii makes it possible to significantly reduce the stress levels in the ceramic material: on batches produced under equivalent conditions (parameters and machining conditions, manufacturing range), an increase in the breaking force of the axis stressed in 3-point bending (with the force bearing point on the balance receiving zone) and a reduction in the number of axes broken during standardized impacts were measured:.

[0130] - In a first series of tests on 10 parts, the radius of curvature in the connection zones was increased from 35 pm to 55 pm, and resulted in an increase in breaking force from 12N to 16N and a very significant reduction in the rate of broken axes from 50% to 0%;

[0131] - In a second series of tests on 10 parts, the radius of curvature in the connection zones was increased from 10 pm to 55 pm, and resulted in an increase in breaking force from 7-1 ON to 15N and a very significant decrease in the rate of broken axes from 70% to 0%.

[0132] An increase in the radius to 40pm, or even greater than 50pm, thus makes it possible to gain 50% on the breaking force and to avoid breakage of the shaft during impacts made in motion with the assembled balance wheel.

[0133] The pivots, which absorb the forces exerted on the balance spring, are the most critical functional parts. As seen previously, the pivots cooperate with the bearings to ensure the most regular and efficient oscillation of the balance spring, minimizing friction losses (the same is true for the rotation of the escape wheel or the back and forth movement of the anchor). Friction losses, and therefore the accuracy of the watch, will be all the better if the diameter at the pivots is small. On the other hand, a small diameter results in low mechanical resistance, and therefore high sensitivity to shocks.For most metal alloys used for axles, and especially for non-magnetic alloys, the deformation behavior shows a plastic deformation domain: an impact can cause irreversible deformation, which leads to a lack of concentricity of the axle and a deterioration of chronometric performance. A ceramic axle will not (or very little) deform plastically, and too much deformation will cause the axle to break and the watch to stop. There is therefore a compromise to be found between the precision of the watch (smallest possible diameter) and the mechanical strength of the axle (largest possible diameter). Obtaining a functional ceramic axle that can withstand the stresses of the watch under demanding conditions is therefore a real challenge.

[0134] As seen previously, first parts 13 (ends of the watch axis 1) ensure contact with the counter-pivot stone 59. These contacts occur for example in horizontal positions of the movement (axis of rotation of the axis parallel to the Earth's gravity).

[0135] As seen previously, second parts 12 (pivots 12) ensure the contact of the axis 1 with the pivot stones 50, on which the surfaces of the pivots come to bear, in particular in vertical and inclined positions of the movement. The pivots each comprise a first portion of surface of revolution (obtained by revolution of a first portion 121 of generating curve G) which is, as mentioned previously, intended to come into contact with a pivot stone 50.

[0136] The axis 1 further comprises at least one connection zone comprising a second portion of surface of revolution (obtained by revolution of a second portion 122 of the generating curve G). Each connection zone makes it possible to connect a pivot to a truss rod 14 or directly to the body 15 of the axis 1 in the absence of a truss rod. The studies carried out show that these connection zones are important for mechanical strength.

[0137] According to the prior art, the axial sections (relative to the axis A1) of the first surface portion are rectilinear: the first surface portions are cylindrical or frustoconical. This geometry is due in large part to the machining method used to produce the pivots, and in particular rolling, which does not allow any freedom to produce varied shapes. According to the invention, the use of laser machining makes it possible to produce first surface parts with axial sections (relative to the axis A1) of the first surface portion which are non-rectilinear.

[0138] According to a first embodiment, the generator G comprises at all points a radius of curvature less than 2 mm, in particular less than 1.8 mm.

[0139] According to a second embodiment variant, possibly combinable with the first variant, the diameter of the cross-section of the surface of revolution increases continuously as one moves away from the proximal end 13 of the watch axis 1 and approaches the distal end of the watch axis 1. The proximal end of the axis is the end 13 of the watch axis 1 which is closest to the surface of revolution (along the axis A1). The distal end of the axis is the end 13 of the watch axis 1 which is furthest from the surface of revolution (along the axis A1).

[0140] According to a third embodiment variant, possibly combinable with the first and / or with the second variant, the generator G has a radius of curvature which decreases as one moves away from the proximal end 13 of the clock axis 1 and approaches the distal end of the clock axis 1 (along the axis A1).

[0141] In a particular embodiment, the generator G may have, at the pivot, a first portion 121 seen convexly from the first axis of rotation A1. The tangents to the first portion are between the first portion and the axis A1. The second derivative of the first portion 121 relative to the axis A1 as one moves away from the proximal end of the clock axis 1 and approaches the distal end of the clock axis 1 is strictly positive.

[0142] In an alternative embodiment, the generator G may have, at the pivot, a first portion 121 seen concave from the first axis of rotation A1. The first portion is located between the tangents to the first portion and the axis A1. The second derivative of the first portion 121 relative to the axis A1 as one moves away from the proximal end of the clock axis 1 and approaches the distal end of the clock axis 1 is strictly negative.

[0143] Preferably, in this alternative embodiment, the distance R from the first portion 121 to the first axis of rotation A1 increases according to the following law as a function of the distance d to the proximal end 13 of the clock axis 1: R = A x (d+B) 1 / 3 , with A and B constant numbers. The distance R is therefore the radius of the cross-section (perpendicular to the axis A1 ) located at the distance d from the proximal end 13 of the clock axis 1 . It is interesting to note that with such a dimensioning, the pivot could be longer without increasing the maximum stress. This would allow the pivot to flex more and limit the axial displacement.

[0144] Whichever embodiment is chosen from the two just mentioned, the first portion 121 may be a portion of a circle or an arc of a circle having a first radius of curvature R1.

[0145] Furthermore, whatever the embodiment, the generator G advantageously has a second portion 122 seen convex from the first axis of rotation A1. The tangents to the second portion are between the second portion and the axis A1. The second derivative of the second portion 122 relative to the axis A1 as one moves away from the proximal end of the clockwork axis 1 and approaches the distal end of the clockwork axis 1 is strictly positive. Advantageously again, the first and second portions are connected continuously (same radius R at the connection of the first and second portions), in particular continuously in tangency (same tangent at the connection of the first and second portions) and / or continuously in curvature (same curvature at the connection of the first and second portions).

[0146] The second portion 122 may be a portion of a circle or an arc of a circle having a second radius of curvature R2.

[0147] As an alternative to producing the first and second portions in the form of an arc of circles, the generator G may be constituted by a spline curve, or by portions of spline curves connected continuously, in particular continuously in tangency and / or continuously in curvature.

[0148] With such geometries, the tests carried out by the inventors show a very clear improvement compared to the traditional geometry, which is formed by a truncated pivot connected to a tigeron by a circular arc fillet. The reduction in stresses is estimated at 10% by simulation, with a comparable axial play of the watch axis 1 in the pivot stones.

[0149] It is still possible to reduce the constraints by reducing the axial play.

[0150] Tests were conducted to compare optimized pivots as described above and standard truncated watch axis pivots made of ZrC. It appears that the optimized pivots allow a 24% reduction in stresses in watch axis 1 compared to a watch axis equipped with standard pivots. Furthermore, it appears that the optimized pivots allow a 30% increase in breaking force compared to a watch axis equipped with standard pivots.

[0151] The inventors have found that the central part (or body 15) of the watch staff 1, i.e. the part 11 including in particular the stems and the plate or seat which accommodates the hub of the balance wheel, the collet of the balance spring, and / or the single or double-plate, also includes potential areas of weakness, in particular if the staff is made of ceramic material. It turns out that the traditional elements of the construction of a balance staff, such as the bearing surfaces, or the abrupt changes in dimension, detract from the strength of the staff when it is made of ceramic material. Certain characteristics, which do not pose any problem with a high-performance metal alloy, turn out to be critical points of weakness with a technical ceramic. ZI

[0152] As with pivots, inventors have found that corners and edges, which promote stress concentrations, should generally be avoided. Geometries, particularly those for receiving the various elements assembled on the axis, must be optimized to lower stress levels. Generally speaking, it is advisable to use curvature radii of at least 20 pm, or preferably at least 50 pm, for connection radii in order to minimize stresses.

[0153] A first solution to limit the constraints and increase the resistance of the axle between the pivots is to use a conical support surface for some of the elements assembled on the axle, as illustrated below in a non-limiting manner with the example of a double chainring.

[0154] In the case of a traditional assembly of a double plate, the double plate has a bore with entry chamfers on either side which facilitate its machining and assembly by driving onto the axis. The double plate is driven in, resting on a bearing surface provided on the watch axis 1, and the chamfer does not cooperate with the axis: there remains a space between:

[0155] - the chamfer of the double-tray, and

[0156] - the connection radius on the axis between the receiving part and the bearing.

[0157] In the case of the optimized geometry, the double-plate 3 has a truncated cone-shaped bearing surface 31 which is larger than a simple chamfer or a simple beveled edge. This surface 31 bears directly on a corresponding truncated cone-shaped surface 21 made on the watch shaft 1. Ideally, the angle of the two corresponding surfaces is identical or comparable, in order to obtain controlled positioning of the assembled component on the watch shaft 1. This arrangement makes it possible to control the position of the double-plate with a well-defined stop, while avoiding abrupt variations in the section of the balance staff, and therefore minimizing the stresses in the staff.The creation of a support on a cone, for example a 45° cone, also allows for better holding of the double-plate during impacts, which tend to cause a relative displacement of the watch axis 1 and the double-plate 3 relative to the driving axis A1, in particular around the driving axis A1.

[0158] Tests were carried out with a nominal height and width of the truncated cone-shaped bearing surface 31 of 0.07 mm (on the assembled component side), and the results are entirely satisfactory, with no problems detected. The dimension of the truncated cone-shaped bearing surface 31 must be adapted to the strength of the double-plate material, because a reduction in the width of the truncated cone-shaped bearing surface 31 increases the risk of the double-plate material being damaged during impacts. This dimension of the truncated cone-shaped bearing surface 31 is estimated at:

[0159] - 0.05 mm width (measured along the A1 axis) and / or height (measured perpendicular to the A1 axis) for heavy balances (typical dimensions and inertia for a large diameter movement, > 25 mm), and

[0160] - 0.04 mm in width (measured along the A1 axis) and / or height (measured perpendicular to the A1 axis) for light balances (small diameter movement, < 25 mm).

[0161] In any case, it seems recommended that the truncated conical bearing surface 31 on the double-plate is not less than that guaranteeing the absence of matting or low matting of the assembled component (for example of the double-plate) during axial impacts.

[0162] Concerning the angle of the truncated cone-shaped support surface 31, the chosen value results from a trade-off between two opposing requirements. To increase the strength of the shaft, the most gradual shape transition or diameter change possible is required, and therefore the smallest possible angle between the axis of revolution and the truncated cone-shaped surface. Overall, an angle between the axis of symmetry and the truncated cone-shaped surface < 45° significantly reduces stresses in the shaft during radial impacts. For the assembled component, on the contrary, the largest possible angle is required to ensure good positioning on the shaft after driving. The compromise chosen is an angle of 45° (half angle at the apex of the cone formed by the truncated cone-shaped section).That being said, a minimum angle of 30° (half-angle at the apex of the cone) allows for good positioning while avoiding a too marked diameter transition on the axis, which would worsen the reinforcement of the axis and the reduction of stresses and would reduce the gain compared to a standard geometry. The other requirement is less critical and will depend on the elastic resistance of the material of the assembled component and the precision of the relative positioning of the different elements (for example, precise chamfers on the assembled component). It appears that an angle of 60° can still be suitable. In conclusion, the ideal angle seems to be 45° (half-angle at the apex of the cone), with an admissible range of 30° to 60° (half-angle at the apex of the cone).

[0163] This type of taper support is to be distinguished from clamping or couplings of the "Morse taper" type (or fitting tapers) or "ISO tapers" which are used in other fields. In these cases the taper of the axis is low, of the order of 3° and less for a "Morse taper".

[0164] A second solution for limiting the constraints, which can be very advantageously combined with the first solution, is to move the receiving or driving portion 24 of the element, for example the double-plate, away from the support or stop portion 21. When mounting the element 3 on the watch axis 1, the element is driven along the axis A1 onto the watch axis 1, in particular onto the driving portion 24, and the element 3 is stopped axially relative to the watch axis 1 when it comes to bear against the support or stop portion 21 of the watch axis 1. The element 3 therefore comprises:

[0165] - a chasing portion 34 cooperating with the receiving or chasing portion 24, and

[0166] - a stop or support portion 31 cooperating with the stop or support portion 21.

[0167] In the case of standard geometry, the driving zone is placed as close as possible to the bearing surface, to facilitate machining and assembly of components, as well as to improve the mechanical strength of the axis.

[0168] The inventors have found that this arrangement is unfavorable in the case of a ceramic shaft or axle: the optimized geometry seeks to move the receiving portion of the component 24 away from the support portion 21 by providing a reduced section area 25 between the receiving portion 24 and the support portion 21, which avoids any contact and clamping of the watch axle 1 near the support portion 21. This makes it possible to avoid the superposition of the stresses linked to the driving in of the element and the stresses linked to the variation in section induced by the presence of the support area 21. This solution is a priori counter-intuitive: in fact, the measurements show that the resistance of the watch axle 1 alone is reduced with this optimized geometry as shown in Figure 3.However, once the element is assembled on the axle, the element-axle assembly is significantly less fragile and more resistant, particularly to shocks, than an element-axle assembly known from the prior art.

[0169] The impact of the central geometry of the shaft (body of shaft 15) was characterized on batches of five components at the double-chainring support. A version with optimized geometry according to the second aspect of the invention was compared to a standard or traditional version (with bearing perpendicular to the axis A1 and adjacent to the driving-in portion of the double-chainring). This characterization is carried out by a 3-point bending test, with a force recovery at each pivot and a force applied at the balance receiving portion, on an assembled sprung balance. The breaking force is 17.3±1.2 N for the standard version and 18.9±0.6 N for the optimized version, a statistically significant difference of 10%. This gain is comparable to that expected from the numerical simulations, and allows additional operating safety and improved shock resistance of the ceramic balance shaft.A gain of the same order of magnitude is also observed for the average drop height causing the breakage of the balance shaft at its central part (severe ram impact test). It is very likely that systematic optimization will make it possible to further improve the gain obtained.

[0170] The purpose of the separation portion between the receiving portion 24 and the support portion 21 is to separate the stress zones generated on the one hand by the driving in, and on the other hand by the variations in cross section, in particular when the watch axis 1 undergoes a bending deformation.

[0171] Simulations were carried out to estimate the minimum dimension L of the separation zone. For a distance L of 0.02 mm between the receiving portion 24 and the support portion 21, the stress fields are merged. A separation occurs for a distance of 0.05 mm, with a stress value reduced by 5%. The separation is well marked for a distance of 0.1 mm, with a stress value reduced by 10% compared to a distance of 0.02 mm.

[0172] The presence of a groove 25 or a separation portion 25 having a diameter smaller than that of the first driving portion 24 and making it possible to separate the first driving portion 24 and the first stopping portion 21, is therefore very beneficial, and is manifested in the simulated case for a distance of 50 pm already, more particularly 100 pm. This separation is achieved by a groove formed on the axis. The depth does not appear to be an influential parameter according to the simulations carried out. The groove depth is for example 7 pm (radius difference of 7 pm between the groove 25 and the portion 24). Complementarily and / or alternatively, a radius difference between the bore 34 of the driven element 3 and the bottom of the groove can be of the order of 4 pm.

[0173] Advantageously, the chasing portion 24 and the separation portion 25 are connected by one or more fillets and / or the first stop portion 21 and the separation portion 25 are connected by one or more fillets.

[0174] A second embodiment of a timepiece according to the invention is described below with reference to Figure 4.

[0175] Preferably, the second embodiment differs from the first embodiment by the geometries of the watch axis 1 and of the element 3 making it possible to separate the portions generating constraints on the watch axis 1.

[0176] Element 3 includes:

[0177] - the second portion 34 of chasing on the clock axis 1, and

[0178] - the second portion 31 of truncated cone-shaped stop arranged to stop the element 3 when it is driven onto a watch axis 1.

[0179] The second stop portion has a half-angle at the apex of between 30° and 60° and the distance L measured along the driving axis A1 and separating the second driving portion 34 from the second stop portion 31 is at least 0.05 mm, or even at least 0.1 mm. In order to obtain this distance, the element 3 preferably comprises a recess 35 between the second driving portion 34 and the second stop portion 31 as shown in FIG. 4. As an alternative to the recess 35, a conical bored portion may be produced to connect the portions 31 and 34.

[0180] With such an embodiment, we note that it is not necessary to provide a groove on the clock axis 1 between the portions 24 and 21.

[0181] Whatever the embodiment or variant, the clock axis 1 is advantageously made of:

[0182] - a technical ceramic, in particular zirconia or alumina, or

[0183] - a glass, in particular a metallic glass, or

[0184] - a steel, in particular a carbon steel, or

[0185] - a paramagnetic austenitic steel, or

[0186] - a metal alloy, or

[0187] - a high entropy alloy, or

[0188] - a composite material, in particular a composite material comprising a ceramic filler in a metal matrix.

[0189] Technical ceramic materials, such as zirconia or alumina, have interesting mechanical characteristics and properties for many applications. However, their implementation for watch movement components is difficult, particularly due to the challenge of obtaining small components with very tight tolerances and the brittleness of the material. These two obstacles are particularly limiting for the use of ceramics at the level of the movement axes, particularly the balance staff, although their high hardness and paramagnetic character make them a material of choice. Nevertheless, the axis geometries of the solutions described above prove to be particularly suitable for ceramic materials, with optimizations made to the pivots and the body of the staff that significantly increase the strength and breaking force of the axes.These new geometries facilitate the use of ceramic axes by ensuring that the watch movement meets demanding shock resistance specifications.

[0190] Whatever the embodiment or variant, the watch axis may have several surfaces of revolution and the surfaces of revolution of the watch axis 1 around the first axis of rotation A1 each have a generator which, in the plane P passing through the first axis of rotation or driving A1, has a radius of curvature greater than 40 pm or 50 pm at any point of the generator.

[0191] Whatever the embodiment or variant, the clockwork axis 1 advantageously has a geometry of revolution around the driving or rotation axis A1.

[0192] Regardless of the embodiment or variant, the stop and / or chase portions may not be circular.

[0193] Whatever the embodiment or variant, the transverse dimension, in particular the diameter, of the driving portion may be between 0.2 mm and 1 mm, or even between 0.2 mm and the maximum diameter of the watch axis reduced by the width of the bearing surface 21. Preferably, the driving portion and / or the receiving portion are of cylindrical geometry, in particular with a constant or substantially constant diameter. Preferably, whatever the embodiment or variant, the axial dimension (measured parallel to the geometric axis A2) of:

[0194] - the driving portion 24 is greater than 0.1 mm or 0.1 times, or even 0.25 times, the driving diameter, and / or

[0195] - the driving portion 34 is greater than 0.1 mm or 0.1 times, or even 0.25 times, the driving diameter.

[0196] More preferably, whatever the embodiment or variant, the contact between:

[0197] - the hunting portion 24, and

[0198] - the driving portion 34 is not linear (annular). This contact does not have the shape of a curve, but of a surface. The same applies to the shape of the driving portions 24 and 34.

[0199] In the embodiment shown, the stop portions 21, 31 are conical or frustoconical. Alternatively, whatever the embodiment or variant, the stop portions 21, 31 may be planar.

[0200] The embodiments or variants have been described applied to the driving of a double-plate onto a balance staff. Nevertheless, the solutions described are applicable to mounting any type of element onto any type of watch staff, such as for example a balance spring collet onto a balance staff, a balance wheel onto a balance staff, an anchor plate onto an anchor stem, an anchor wheel plate onto an escape pinion, or even a mobile plate onto a mobile staff or pinion.

[0201] Document EP3258325A1 describes a watch shaft, and in particular a balance shaft, made of a naturally paramagnetic ceramic material. The advantage of ceramic is that the pivots do not mark during significant impacts, unlike pivots made of metal alloys which can deform plastically. In addition, the work of the applicant of application EP3258325A1 has shown that ceramic shafts do not wear during operation, probably due to their high hardness, which allows performance to be maintained over time, unlike most paramagnetic metal alloys.

[0202] Thanks to the solutions described above, it is possible to obtain, with a ceramic material, performances equivalent to those of the alloys traditionally used to make watch axes. Indeed, with the same axis geometry, the fragile behavior of a ceramic intrinsically leads to a lower resistance than that of the best ferromagnetic alloys such as 20AP steel.

[0203] The developments carried out have enabled in particular:

[0204] - By optimizing the shape of the pivots, to gain 25% on the maximum breaking strength constraint.

[0205] - By changing the design of the axle, and in particular the use of gradual variations in section, large connecting radii, the introduction of a conical support surface for some of the elements attached to the axle, the distance between the receiving / driving portion and the support portion, to increase the breaking force by 10%.

[0206] The solutions described also make it possible to improve the mechanical performance of watch axes made from materials other than ceramic.

[0207] Throughout this document, by "fillet" is meant, in a part of any shape, a rounding connecting two surfaces, for example two cylindrical surfaces of different diameters. What watchmakers call the cone of a conical pivot is in reality often a fillet connecting the pivot to the rest of the watch axis.

[0208] Throughout this document, "span" means any surface of a watch axis that is not parallel to the longitudinal direction of the watch axis and that allows an element attached to the watch axis to be stopped. Unless otherwise specified, "span" means a flat surface perpendicular to the longitudinal direction of the watch axis.

Claims

Claims:

1. Assembly (150), in particular assembled balance (150), comprising: - a clock axis (1), and - an element (2; 3; 4) driven onto the watch axis (1), the watch axis (1) having a first driving portion (24) and a first stopping portion (21) arranged to stop the element (2; 3; 4) when it is driven onto the watch axis (1), the element (2; 3; 4) having a second driving portion (34) onto the watch axis (1) and a second stopping portion (31) arranged to stop the element (2; 3; 4) when it is driven onto the watch axis (1), the first driving portion (24) and the first stop portion (21) being separated by a separation portion (25) having a diameter smaller than that of the first driving portion (24), and / or the element (2; 3; 4) comprising a recess (35) between the second driving portion (34) and the second stop portion (31).

2. Assembly (150) according to claim 1, characterized in that the first stop portion (21) is frustoconical and has, for example, a half-angle at the apex of between 30° and 60° and / or in that the distance (L) measured along the driving axis (A1) and separating the first driving portion (24) from the first stop portion (21) is at least 0.05 mm, or even at least 0.1 mm.

3. Assembly (150) according to claim 1 or 2, characterized in that the clockwork axis is a balance wheel axis (2). Assembly (150) according to one of the preceding claims, characterized in that the first driving portion (24) and the separation portion (25) are connected by one or more fillets and / or in that the first stop portion (21) and the separation portion (25) are connected by one or more fillets. Assembly (150) according to one of the preceding claims, characterized in that the watch axis (1) is made of: - a technical ceramic, in particular zirconia or alumina, or - a glass, in particular a metallic glass, or - a steel, in particular a carbon steel, or - a paramagnetic austenitic steel, or - a metal alloy, or - a high entropy alloy, or - a composite material, in particular a composite material comprising a ceramic filler in a metal matrix. Assembly (150) according to one of the preceding claims, characterized in that the watch axis (1) has a geometry of revolution around the driving axis (A1). Assembly (150) according to one of the preceding claims, characterized in that the watch axis (1) has surfaces of revolution around the driving axis (A1) and in that the surfaces of revolution each have a generatrix which, in a plane (P) passing through the driving axis (A1), has a radius of curvature greater than 40 pm or 50 pm at any point of the generatrix. Assembly (150) according to one of the preceding claims, characterized in that the watch axis (1) comprises at least one pivot (12), preferably two pivots. Assembly (150) according to one of the preceding claims, characterized in that the second stop portion is frustoconical and has a half-angle at the apex of between 30° and 60° and / or in that the distance (L) measured along the driving axis (A1) between the second driving portion (34) and the second stop portion (31) is at least 0.05 mm, or even at least 0.1 mm. Assembly (150) according to one of the preceding claims, characterized in that the element (2; 3; 4) is a balance wheel (2) or a plate or a double plate (3) or a collet (4). Watch movement (200) comprising an assembly according to one of claims 1 to 10. Timepiece (300), in particular wristwatch, comprising: - a clock movement (200) according to the preceding claim, and / or - an assembly (150) according to one of claims 1 to 10. A watch spindle (1) comprising a first portion (24) for driving an element (2; 3; 4) along a driving axis (A1), the watch spindle (1) having a geometry: having a first frustoconical stop portion (21) arranged to stop an element (2; 3; 4) during its driving onto the watch spindle (1), the first stop portion (21) having a half-angle at the apex of between 30° and 60°, and such that the distance (L) measured along the driving axis (A1) and separating the first portion (24) from driving of the first stop portion (21) is at least 0.05 mm, or even at least 0.1 mm. Watch shaft (1) according to claim 13, characterized in that the watch shaft is a balance shaft (2). Watch shaft (1) according to one of claims 13 and 14, characterized in that the first driving portion (24) and the first stop portion (21) are separated by a separation portion (25) having a diameter smaller than that of the first driving portion (24). Watch shaft (1) according to the preceding claim, characterized in that the first driving portion (24) and the separation portion (25) are connected by one or more fillets and / or in that the first stop portion (21) and the separation portion (25) are connected by one or more fillets. Watch axis (1) according to one of claims 13 to 16, characterized in that the axis is made of: - a technical ceramic, in particular zirconia or alumina, or - a glass, in particular a metallic glass, or - a steel, in particular a carbon steel, or - a paramagnetic austenitic steel, or - a metal alloy, or - a high entropy alloy, or - a composite material, in particular a composite material comprising a ceramic filler in a metal matrix. Watch shaft (1) according to one of claims 13 to 17, characterized in that the watch shaft (1) has a geometry of revolution around the driving axis (A1). Watch shaft (1) according to one of claims 13 to 18, characterized in that the watch shaft (1) has surfaces of revolution around the driving axis (A1) and in that the surfaces of revolution each have a generatrix which, in a plane (P) passing through the driving axis (A1), has a radius of curvature greater than 40 pm or 50 pm at any point of the generatrix. Watch shaft (1) according to one of claims 13 to 19, characterized in that the watch shaft (1) comprises at least one pivot (12), preferably two pivots. Element (2; 3; 4) intended to be driven onto a watch axis (1) along a driving axis (A1), the element (2; 3; 4) comprising: - a second portion (34) of chasing on a clock axis (1), and - a second truncated cone-shaped stop portion (31) arranged to stop the element (2; 3; 4) when it is driven onto a watch axis (1), the second stop portion having a half-angle at the apex of between 30° and 60°, the distance (L) measured along the driving axis (A1) between the second driving portion (34) and the second stop portion (31) being at least 0.05 mm, or even at least 0.1 mm. Element (2; 3; 4) according to the preceding claim, characterized in that the element (2; 3; 4) is a balance wheel (2) or a plate or a double plate (3) or a collet (4). Element (2; 3; 4) according to claim 21 or 22, characterized in that the element (2; 3; 4) comprises a recess (35) between the second driving portion (34) and the second stopping portion (31). Assembly (150), in particular assembled balance (150), comprising: - a watch axis (1), in particular a watch axis (1) according to one of claims 13 to 20, and - an element (2; 3; 4) driven onto the clockwork axis (1), in particular an element (2; 3; 4) according to one of claims 21 to 23. Clockwork movement (200) comprising: - a watch axis (1) according to one of claims 13 to 20, and / or - an element (2; 3; 4) according to one of claims 21 to 23, and / or - an assembly according to claim 24. Timepiece (300), in particular wristwatch, comprising: - a clock movement (200) according to the preceding claim, and / or - a watch axis (1) according to one of claims 13 to 20, and / or - an element (2; 3; 4) according to one of claims 21 to 23, and / or - an assembly (150) according to claim 24. Watch axle (1), in particular axle for balance wheel (2) or axle for escape wheel or axle for anchor, comprising: - a first axis of rotation (A1), and - at least one pivot (12), the clockwork axis (1) having a surface of revolution around the first axis of rotation (A1), the generator (G) of which, in a plane (P) passing through the first axis of rotation (A1), is curved, this surface of revolution extending at least at the level of the pivot, the pivot being defined as the area of ​​the watch axis (1) intended to come into contact with a pivot bearing (50), in particular with a pivot stone (50). Watch axis (1) according to claim 27, characterized: - in that the generator (G) comprises at all points a radius of curvature less than 2 mm, in particular less than 1.8 mm, and / or - in that the diameter of the cross-section of the surface of revolution increases continuously as one moves away from the proximal end (13) of the clockwork axis (1), and / or - in that the generator (G) has a radius of curvature which decreases as one moves away from the proximal end (13) of the watch axis (1). Watch axis (1) according to one of claims 27 and 28, characterized in that the generator (G) has, at the pivot, a first portion (121) seen convexly from the first axis of rotation (A1). Watch axis (1) according to one of claims 27 and 28, characterized in that the generator (G) has, at the pivot, a first portion (121) seen concavely from the first axis of rotation (A1). Clock axis (1) according to claim 30, characterized in that the distance R from the first portion to the first axis of rotation (A1) increases according to the following law as a function of the distance d to the proximal end (13) of the clock axis (1): R = A x (d+B) 1 / 3 , with A and B constant numbers. Watch axis (1) according to claim 29 or 30, characterized in that the first portion (121) is a portion of a circle having a first radius of curvature (R1). Watch axis (1) according to one of claims 29 to 32, characterized in that the generatrix (G) has a second portion seen convex (122) from the first axis of rotation (A1), the first and second portions being connected continuously, in particular continuously in tangency and / or continuously in curvature. Watch axis (1) according to the preceding claim, characterized in that the second portion (122) is a portion of a circle having a second radius of curvature (R2). Watch axis (1) according to one of claims 27 to 34, characterized in that the generator (G) consists of a spline curve, or portions of spline curves connected continuously, in particular continuously in tangency and / or continuously in curvature.Watch axis (1) according to one of claims 27 to 35, characterized in that the watch axis has several surfaces of revolution and in that the surfaces of revolution of the watch axis (1) around the first axis of rotation (A1) each have a generatrix which, in a plane (P) passing through the first axis of rotation (A1), has a radius of curvature greater than 40 pm or 50 pm at any point of the generatrix. Watch axis (1) according to one of claims 27 to 36, characterized in that the watch axis (1) is made of:. - a technical ceramic, in particular zirconia or alumina, or - a glass, in particular a metallic glass, or - a steel, in particular a carbon steel, or - a paramagnetic austenitic steel, or - a metal alloy, or - a high entropy alloy, or - a composite material, in particular a composite material comprising a ceramic filler in a metal matrix. Assembly (150), in particular assembled balance wheel (150), comprising a watch shaft (1) according to one of claims 27 to 37. Assembly (100) comprising: - a watch axis (1) according to one of claims 27 to 37 or an assembly (150) according to claim 38, and - a pivot bearing (50), in particular a pivot stone (50). Assembly (100) according to the preceding claim, characterized in that the pivot bearing (50) includes a pivot stone (50) comprising a hole (51) along a second axis of rotation (A2) for pivoting the watch axis (1), the hole comprising: - a first pivoting zone (52) of the clock axis (1), and - a second clearance zone (53) extending from a first face (54) of the bearing to the first pivot zone (52), the face (54) being perpendicular or substantially perpendicular to the second axis of rotation (A2) and intended to be oriented towards the body of the watch axis (1), the first pivot zone (52) and the second clearance zone (53) connecting to each other by a connecting rounded part (55). Assembly (100) according to the preceding claim, characterized in that the second clearance zone (53) comprises a maximum diameter greater than twice or greater than four times or greater than six times the minimum diameter of the first pivot zone (52). Watch movement (200) comprising a watch axis (1) according to one of claims 27 to 37 and / or an assembly according to claim 38 and / or an assembly according to one of claims 39 to 41. Timepiece (300), in particular a wristwatch, comprising a watch movement (200) according to the preceding claim and / or a watch axis (1) according to one of claims 27 to 37 and / or an assembly according to claim 38 and / or an assembly according to one of claims 39 to 41.

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