Part for fastening a timepiece hairspring

Abstract

Peg (1) for fixing one end of a spiral spring, the peg comprising a first portion (10) intended to come into contact with the spiral spring, the first portion being shaped so as to present a first surface (10b) and a second surface (10c) for bearing with the spiral spring.

Description

[0001] The invention relates to an assembly comprising a balance spring and a stud. The invention further relates to an oscillator or a watch movement or a watch component comprising such an assembly. Finally, the invention relates to a method for manufacturing such an assembly. Mechanical oscillating watch mechanisms, comprising a balance spring, are generally equipped with a ferrule for securing the inner end of the balance spring and / or a stud for securing the outer end of the balance spring. In the case of a balance spring made of a paramagnetic alloy comprising at least one of the elements Nb, V, Ta, Ti, Zr, Hf, the securing piece for the balance spring, namely the ferrule or the stud, can be attached to the balance spring by welding, in particular by laser welding. Generally, this securing piece is made of steel, particularly stainless steel.Such an assembly solution gives satisfaction in the case of welding a spiral spring made of a paramagnetic Nb-Zr-O alloy such as that protected by patent EP0886195B1.

[0002] Application CH706846 relates more specifically to a split ferrule made of a titanium-based material. The low density of titanium is exploited to create a ferrule with minimized density, thereby improving the isochronism of the oscillator in which the ferrule is used. However, document CH706846 discloses a ferrule with a completely conventional structure, featuring first and second flats. The ferrule is laterally drilled to receive the inner end blade of a balance spring. This blade can be fixed conventionally, either by pinning or, alternatively, by welding, particularly laser welding. Nevertheless, no geometric adaptation of the receiving surface is proposed to enable, or even optimize, the welding of the balance spring within the ferrule's groove.Furthermore, no details are given regarding the nature of the material of the spiral spring intended to be attached to such a ferrule.

[0003] It is known to attach a spiral spring to a ferrule or stud by laser welding. Patent application CH561921, for example, discloses a laser welding method for a ferrule that includes a preliminary pre-fixing step for the spiral spring to precisely position it relative to the ferrule.

[0004] Application FR2017027 specifically concerns the laser welding of the inner end of a spiral spring to a portion of a ferrule shaped like an arc of a circle centered on the spiral spring's axis of rotation. No details are provided regarding the nature of the materials used in the device. The leaf portion of the inner end of the spiral spring rests continuously against the ferrule portion. A single weld point is defined along the contact line between the spiral and the ferrule. To mitigate the risk of weld failure, it is recommended to adjust the laser intensity so that the weld point does not exceed half the height of the leaf and extends over a length at least equal to the height of the leaf. However, such a configuration does not eliminate the formation of brittle intermetallic compounds that contribute to weld embrittlement.Furthermore, such a conformation also risks creating heating of the spring blade of the balance spring and therefore a possible modification of its mechanical properties, as well as undesirable unsightly effects.

[0005] Patent CH468662 discloses a specific ferrule geometry, which features an annular groove designed to support and guide the inner end blade of the spiral spring. This design prevents thermal conduction from being interrupted between any two welded areas if the leaf spring is attached to the ferrule by welding, particularly laser welding.

[0006] US patent 3016688, for its part, discloses an elastic stud comprising a flat surface onto which a portion of the outer end of a balance spring is welded. The description indicates that the stud can be welded at several points, including more than two. No mention is made of the materials used in the device; however, it is stated that such a solution would strengthen the balance spring's attachment to the stud. Nevertheless, such a configuration does not eliminate the possibility of brittle intermetallic compounds that could weaken one or more of the weld points, potentially leading to weakening of the balance spring's mounting and thus a variation in the chronometry, particularly the isochronism slope, of the oscillator in which such a device is used.Furthermore, the geometry of such a pin does not allow for breaking the thermal conduction between two weld points.

[0007] The use of balance springs comprising at least one of the elements Nb, V, Ta, Ti, Zr, Hf, is also known from the prior art. Patent EP0886195B1, for example, discloses a balance spring made of a paramagnetic Nb-Zr alloy comprising between 5% and 25% by mass of Zr, as well as an interstitial doping agent formed at least in part of oxygen.

[0008] Patent EP1258786B1 also discloses a spiral made of Nb-Hf paramagnetic alloy comprising between 2% and 30% by mass of Hf.

[0009] Application WO2015189278, for its part, discloses a balance wheel and hairspring in which the hairspring is made of a titanium alloy comprising, in particular, a titanium base containing between 10 at.% and 40 at.% of one of the elements Nb, Ta, or V, between 0 at.% and 6 at.% of Zr, and between 0 at.% and 5 at.% of Hf. The document mentions that such a hairspring can be ferrulated and pinned so as to be assembled within an oscillator, without any further details.

[0010] The aim of the invention is to provide a fastening element for one end of a watch balance spring, thereby overcoming the aforementioned drawbacks and improving upon existing prior art fastening elements. In particular, the invention proposes a fastening element that improves the attachment of a balance spring, notably enhancing its resistance to pull-out.

[0011] An assembly comprising a balance spring and a stud according to the present invention is defined by claim 1. A method for manufacturing such an assembly according to the present invention is defined by claim 10. A watch oscillator or a watch movement or a watch component comprising such an assembly according to the present invention is defined by claim 12. Particular embodiments are defined by claims 2 to 9 and 11.

[0012] According to one aspect, a fastener is defined by the following propositions: a. A fastening element, in particular a pin or ferrule, for one end of a paramagnetic alloy spiral spring comprising at least one of the following elements: Nb, V, Ta, Ti, Zr, and Hf, the fastening element comprising a first portion intended to come into contact with the spiral spring and made of titanium or a titanium alloy or tantalum or a tantalum alloy, in particular grade 2 titanium or grade 5 titanium. b. A fastening element according to proposal a, characterized in that the first portion comprises two bearing surfaces separated by a groove, each bearing surface being intended to come into contact with the spiral spring, and the groove extending in particular along the height of the spiral spring, preferably over a height greater than that of the spiral spring. c.A fastening element according to proposition b, characterized in that each surface has, at at least one of its ends in the vertical direction of the balance spring, a positioning conformation extending perpendicularly or substantially perpendicularly to the surface. d. A fastening element according to proposition b, characterized in that each surface has, at two of its ends in the vertical direction of the balance spring, respectively a first positioning conformation and a second positioning conformation, the conformations extending perpendicularly or substantially perpendicularly to said surface. e. A fastening element according to any one of propositions a to d, characterized in that it comprises a second portion intended to come into contact with a stud holder or with a balance staff. f.A fixing piece according to one of propositions a to e, characterized in that the surfaces are arranged substantially perpendicular to a plane of the balance spring and form an angle with each other, in particular an angle between 150° and 179° viewed from an axis of the balance spring. g. A fixing piece according to one of propositions a to e, characterized in that the surfaces are arranged substantially perpendicular to a plane of the balance spring and / or are curved to form parts of the same cylinder of revolution or are tangent to the same cylinder of revolution. h. A fixing piece according to proposition g, characterized in that the fixing piece is a ferrule and in that the cylinder of revolution is centered on an axis of the ferrule. i.A fastening element according to any one of propositions a to h, characterized in that the fastening element is a ferrule and in that the ferrule comprises at least one stop, in particular two, three, four or five stops, distributed angularly, in particular regularly distributed angularly, on an outer periphery of the ferrule.

[0013] According to the first aspect, a manufacturing process is defined by the following propositions: j. A method for manufacturing an assembly comprising a stud according to one of propositions a to g and a paramagnetic alloy spiral spring comprising at least one of the following elements: Nb, V, Ta, Ti, Zr and Hf, the method comprising the following steps: Supply of the stud; Supply of the spiral spring; Fixing of the stud and the spiral spring. k. A method for manufacturing an assembly comprising a ferrule according to one of propositions a to i and a paramagnetic alloy spiral spring comprising at least one of the following elements: Nb, V, Ta, Ti, Zr and Hf, the method comprising the following steps: Supply of the ferrule; Supply of the spiral spring; Fixing of the ferrule and the spiral spring. l.A method for manufacturing an assembly comprising a stud according to one of propositions a to g, a ferrule according to one of propositions a to i, and a spiral spring made of a paramagnetic alloy comprising at least one of the following elements: Nb, V, Ta, Ti, Zr, and Hf, the method comprising the following steps: Supply of the stud; Supply of the spiral spring; Supply of the ferrule; Fixing of the stud and spiral spring, and fixing of the ferrule and spiral spring. m. A manufacturing method according to one of propositions k to l, characterized in that the fixing step is carried out by laser welding.

[0014] According to the first aspect, a set is defined by the following propositions: n. Set comprising: a spiral spring, in particular a paramagnetic alloy spiral spring, in particular a paramagnetic alloy spiral spring comprising at least one of the following elements: Nb, V, Ta, Ti, Zr and Hf, in particular an alloy comprising the elements Nb and Zr with between 5% and 25% by mass of Zr and an interstitial doping agent comprising oxygen; and a stud according to any one of propositions a to g; and / or a ferrule according to any one of propositions a to i.

[0015] According to the first aspect, a clock oscillator, clock movement, or timepiece is defined by the following proposition: o. Clock oscillator, clock movement, or timepiece comprising: an assembly according to proposition n, and / or an assembly obtained by implementing the process according to one of the propositions j to m, and / or a pin according to one of the propositions a to g; and / or a ferrule according to one of the propositions a to i.

[0016] According to a second aspect, a fixing eyelet is defined by the following propositions: aa. A pin for attaching one end of a spiral spring, the pin comprising a first portion intended to come into contact with the spiral spring, the first portion being shaped so as to present a first surface and at least a second bearing surface with the spiral spring. cc. A pin according to proposition aa, characterized in that the first and second surfaces are discontinuous. dd. A pin according to proposition cc, characterized in that the first and second bearing surfaces are separated by a groove, the groove extending in particular along the height of the spiral spring, preferably over a height greater than that of the spiral spring. ee. A pin according to any one of propositions aa to dd, characterized in that each surface has, at one of its ends along the height of the spiral spring, a positioning shape extending perpendicularly or substantially perpendicularly to the surface. ff.A pin according to one of propositions aa to dd, characterized in that each surface has, at two of its ends in the direction of the spiral spring's height, respectively a first positioning conformation and a second positioning conformation, the conformations extending perpendicularly or substantially perpendicularly to said surface. gg. A pin according to one of propositions aa to ff, characterized in that it comprises a second portion intended to come into contact with a pin holder. hh. A pin according to one of propositions aa to gg, characterized in that the first and second surfaces are planar or cylindrical, in particular cylindrical of revolution. ii.A pin according to one of propositions aa to hh, characterized in that the first and second surfaces are arranged substantially perpendicularly to a plane of the spiral spring and / or form an angle with each other, in particular an angle between 150° and 179° viewed from an axis of the spiral spring. jj. A pin according to one of propositions aa to ii, characterized in that the first and second surfaces are arranged substantially perpendicularly to a plane of the spiral and / or are formed with a curvature to form parts of the same cylinder of revolution or are made tangent to the same cylinder of revolution. kk. A pin according to one of propositions aa to jj, characterized in that at least one of the first and second surfaces forms a non-zero angle with respect to a plane extending parallel and orthoradially with respect to the axis of the spiral spring.

[0017] According to the second aspect, a process is defined by the following propositions: II. A method for manufacturing an assembly comprising a hook according to one of propositions aa to kk and a spiral spring, the method comprising the following steps: Supply of the hook; Supply of the spiral spring; Fixing of the hook and spiral spring at the first and second surfaces. mm. A manufacturing method according to proposition II, characterized in that the fixing step is carried out by laser welding.

[0018] According to the second aspect, a set is defined by the following proposition: nn. Set comprising: a spiral spring; and a pin according to one of the propositions aa to kk.

[0019] According to the second aspect, a clock oscillator, clock movement, or timepiece is defined by the following proposition: A clock oscillator, clock movement, or timepiece comprising: a set according to proposition nn, and / or a set obtained by implementing the process according to one of propositions Il and mm, and / or a piton according to one of propositions aa to kk.

[0020] According to a third aspect, a fastener for one end of a spiral spring, in particular a stud or ferrule, comprises a first portion intended to come into contact with the spiral spring. This first portion includes two bearing surfaces separated by a groove, each bearing surface being intended to come into contact with the spiral spring. The groove extends, in particular, along the height of the spiral spring, preferably over a height greater than that of the spiral spring.

[0021] Except for technical or logical incompatibility, all the features and / or particularities of the first, second and third aspects of the invention may be combined provided that this combination satisfies the definition of the invention as defined in the claims.

[0022] The attached figures represent, by way of example, an embodiment of a watch part incorporating an embodiment of a stud according to the invention and an embodiment of a ferrule according to the invention. There figure 1 is a front view of an embodiment of a hook used in the present invention. figure 2 is a perspective view of an embodiment of a piton used in the present invention. figure 3 is a partial perspective view of an oscillator according to the invention. figures 4 to 6 These are detailed views of an embodiment of a hook used in the present invention. figures 7 to 11illustrate one method of manufacturing a ferrule. The figure 12 is a diagram representing an embodiment of a timepiece according to the invention. figure 13 is a graph illustrating the improvements in the resistance to pull-out of the spiral spring on a stud according to the invention. figure 14 illustrates a graph representing the average rate (M) of a timepiece, averaged according to the different positions of the timepiece, as a function of the amplitude (A) of the balance wheel-spring in free isochronism.

[0023] An embodiment of a 600 timepiece is described below with reference to the figure 12The timepiece is, for example, a watch, in particular a wristwatch. The timepiece includes a watch movement 500, in particular a mechanical movement, itself comprising an oscillator 400, such as a balance-spring type oscillator comprising a balance wheel pivoted about an axis A1 and a balance spring arranged mainly in a plane P1 perpendicular to the axis A1. The axis A1 is also the axis of the balance spring. The oscillator 400 comprises a balance spring assembly 300, itself comprising a balance spring 2, a first fitting 1' for attaching the inner end 2b of the balance spring to a balance staff, i.e., a ferrule 1', and a second fitting 1 for attaching the outer end 2a of the balance spring to a movement frame, in particular to a balance bridge 4, possibly by means of a stud holder or stud support 3 as illustrated in the figure 3 The second fixing piece is a hook.

[0024] Advantageously, the spiral spring is made of a paramagnetic alloy comprising at least one of the following elements: Nb, V, Ta, Ti, Zr, and Hf. In particular, the spiral spring comprises at least 2%, or even at least 5%, by mass of one of the following elements: Nb, V, Ta, Ti, Zr, and Hf. Preferably, the spiral spring is made of an alloy comprising the elements Nb and Zr with between 5% and 25% by mass of Zr and an interstitial doping agent comprising oxygen. Preferably, the spiral spring is made of an alloy comprising 85% by mass of Nb, 14.95% by mass of Zr, and 0.05% by mass of oxygen. The alloy may further comprise various impurities, for example, within the following limits: Hf < 7000 ppm, Ta < 1000 ppm, W < 300 ppm, Mo < 100 ppm, other < 60 ppm.

[0025] Preferably, the pin 1 includes a portion 10 intended to come into contact with the spiral spring 2. Advantageously, the pin is made: in titanium, or in titanium alloy, in particular in grade 2 titanium or grade 5 titanium, or in tantalum, or in tantalum alloy.

[0026] Similarly, preferably, the ferrule 1' includes a portion 10' intended to come into contact with the spiral spring 2. Advantageously, the ferrule is made: in titanium, or in titanium alloy, in particular in grade 2 titanium or grade 5 titanium, or in tantalum, or in tantalum alloy.

[0027] By "titanium", we preferably mean any material whose mass content of titanium is greater than 99%, or even greater than 99.5%.

[0028] By "titanium alloy" we preferably mean any other material in which the major or dominant element by mass is titanium, such as for example Grade 5 Titanium (Ti6Al4V).

[0029] By "tantalum", we preferably mean any material whose tantalum mass content is greater than 99%, or even greater than 99.5%.

[0030] By "tantalum alloy" we preferably mean any other material in which the major or dominant element by mass is tantalum, such as for example tantalum TaW containing between 2.5% and 10% W by mass or tantalum TaNb containing about 40% Nb by mass.

[0031] The fabrication of the ferrule and / or stud in titanium or titanium alloy is particularly suitable for welding to a spiral spring made of a niobium-based alloy containing between 5% and 25% Zr by mass, specifically an alloy comprising the elements Nb and Zr with between 5% and 25% Zr by mass and an interstitial dopant containing oxygen. Indeed, Nb and Zr are completely soluble in Ti.

[0032] The fabrication of the ferrule and / or stud in tantalum or tantalum alloy is particularly suitable for welding to a spiral spring consisting of a titanium base containing between 17% and 62% by mass of either Nb or Ta, for example, a minimum of 17% Nb and a maximum of 62% Ta. The fabrication of the ferrule and / or stud in tantalum or tantalum alloy is advantageous for welding to an Nb-Hf spiral spring containing between 2% and 30% Hf by mass.

[0033] An embodiment of a piton used in the present invention is described in more detail below with reference to figures 1 to 6 .

[0034] For example, the eye bolt is made in one piece, as in the illustrated embodiment. It generally has a right-angled shape formed by two wings of roughly the same proportions. The two wings can be joined to each other by a radius.

[0035] The pin 1 includes a first portion 10 intended to be welded to the spiral spring 2, in particular by laser welding, at the outer end 2a of the spiral spring as shown in the figure 2 The stud also includes a second portion 100 intended to be fixed, in particular inserted, conventionally within a groove of the stud support 3, which is mounted on the balance bridge 4 as shown in the figure 3 The first and second sections can be made of different materials and mounted one on top of the other.

[0036] The first portion 10 comprises a first bearing surface 10b and a second bearing surface 10c separated by a groove 10a. Each bearing surface is designed to contact the spiral spring. In the illustrated embodiment, the groove extends along the height h of the spiral spring, preferably over a height H10 greater than that of the spiral spring. The groove 10a separates or distinguishes the first and second bearing surfaces 10b, 10c. Advantageously, the groove 10a is oriented substantially along the height H10 of the portion 10 of the pin 1. This configuration prevents any heat conduction during the welding of the spiral blade to each of the first and second bearing surfaces 10b, 10c and avoids creating interference between two heat-affected areas of the spiral spring during welding.This conformation reduces the energy input required for welding and therefore best preserves the integrity of the mechanical properties of the spiral spring alloy.

[0037] The groove can be partially cut into the thickness of the eye bolt, that is, without passing through it. Alternatively, the groove can pass through the entire thickness of the eye bolt.

[0038] Alternatively, as described previously, the groove can be oriented perpendicular to the height h of the spiral spring. The groove can also be oriented in another direction.

[0039] The first bearing surface 10b has, at one of its ends 101b or 102b, a first raised or bulging profile 103b or 104b. This first profile provides a positioning stop for the spiral spring, specifically an axial positioning stop for the spiral spring. The spiral spring blade, in contact with the first surface, can be moved until it comes into contact with this profile, thus precisely positioning the spiral spring relative to the eye pin along the height H10 of the eye pin. The first profile extends, for example, perpendicularly or substantially perpendicularly to the first surface 10b, so as to form a stop. Advantageously, the first bearing surface 10b has, at its other end 101b or 102b, a second raised or bulging profile 103b or 104b. This second conformation allows for the creation of a positioning stop for the spiral spring.The second conformation extends, for example, perpendicularly or substantially perpendicularly to the first surface 10b, so as to form a stop.

[0040] Similarly, the second bearing surface 10c may have, at one of its ends 101c or 102c, a third raised or bulging conformation 103c or 104c. This third conformation provides a positioning stop for the spiral spring. Indeed, the spiral spring blade, in contact with the second surface, can be moved until it comes into contact with the third conformation, thus precisely positioning the spiral spring relative to the pin in the direction of the pin's height H10. The third conformation extends, for example, perpendicularly or substantially perpendicularly to the second surface 10c, so as to form a stop. Advantageously, the second bearing surface 10c has, at the other of its ends 101c or 102c, a fourth raised or bulging conformation 103c or 104c. This fourth conformation provides a positioning stop for the spiral spring.The fourth conformation extends, for example, perpendicularly or substantially perpendicularly to the second surface 10c, so as to form a stop.

[0041] The set of positioning configurations described above allows for precise positioning of the spiral spring blade relative to the pin and, consequently, precise embedding of the spiral spring after welding it to the pin. The weld can be made using two tack welds s1, s2, which are respectively located at each of the bearing surfaces 10b, 10c or at the edge of each of the bearing surfaces 10b, 10c. Preferably, a third and fourth tack weld, s3, s4, are respectively located at each of the bearing surfaces 10b, 10c, or at the edge of each of the bearing surfaces 10b, 10c, in addition to the tack welds s1, s2, as shown in the diagram. figure 2To ensure this precise positioning, when one or two of the bearing surfaces each have two positioning configurations, they are spaced apart by a distance greater than the height h of the spring leaf. Advantageously, this vertical clearance is less than 0.04 mm, or even less than 0.03 mm. The set of positioning configurations described above forms a second groove 10d oriented substantially perpendicular to the first groove 10a, so as to serve as a support and / or guide for the spiral spring leaf, as shown in the figure. figure 1 .

[0042] Advantageously, the first and second bearing surfaces 10b and 10c are designed to perfectly match the curvature of the terminal leaf of the spiral spring. To achieve this, the first and second surfaces 10b, 10c are inclined relative to the surface defined by the bottom of the groove 10a or to the face of the pin visible in the view of the figure 1Preferably, the first and second surfaces 10b, 10c are inclined at two distinct angles, which may, for example, be between 5° and 15°. Consequently, as shown on the figures 5 and 6The first and second surfaces 10b, 10c can form an angle α with each other, specifically an angle α between 150° and 179° viewed from the axis A1 of the balance wheel or balance spring. In other words, the axis A1 lies in the obtuse dihedral angle formed by two half-planes passing through the first and second surfaces, respectively. The first and second surfaces can also be arranged perpendicularly or substantially perpendicularly to the plane P1 of the balance spring. The first and second surfaces can be flat faces. These can be flat faces tangent to the same surface, in particular the same cylinder of revolution or a cylindrical or more complex surface of revolution formed by a portion of the terminal curve of the balance spring. At least one of the first and second surfaces 10b, 10c can form a non-zero angle with respect to a plane extending parallel and orthoradially with respect to the axis A1.

[0043] Alternatively, the first and second surfaces can be curved to best fit the blade of the spiral spring they receive. For example, the first and second surfaces can each constitute a portion of the same cylinder of revolution, or a cylindrical or more complex surface of revolution formed by a portion of the terminal curve of the spiral spring.

[0044] In the embodiment of the pin shown, the first and second surfaces are discontinuous. Ideally, these first and second surfaces are identical to the surface, possibly non-cylindrical, of the outer end 2a of the spiral spring.

[0045] Such a pin configuration advantageously defines at least two point contacts between the pin and the terminal leaf of the spiral spring. The assembly precision, particularly welding, of a spiral spring onto such a pin is thus optimized and is no longer solely determined by the assembly means. In known prior art techniques, assembly means are designed to minimize, before the spiral spring leaf is fixed to the pin, the displacements of the spiral spring leaf around its theoretical point contact, defined exclusively by the curvature of the spring and a single receiving plane for the pin. Due to this degree of freedom, which allows the leaf to oscillate over an angular range of approximately 4°, or even 8°, around its theoretical point contact, a torsional moment of the leaf at the external fixed end of the spiral spring can occur once the leaf is fixed to the pin.Such a phenomenon can contribute to a non-concentric development of the spiral spring and thus induce chronometric disturbances, in particular at the level of the isochronism slope and the "flat-hanging".

[0046] There figure 14 This illustrates a graph representing the average rate M in seconds per day of a timepiece, averaged across the different positions of the timepiece, as a function of the amplitude A in degrees of the balance wheel and hairspring in free isochronism. The dashed curves, corresponding to the isochronism curves for a balance wheel and hairspring assembly representative of the prior art, in which the end of the terminal curve of the hairspring has undergone a displacement of an angle of ±4° around its theoretical point contact with the stud, define an envelope within which the average rate of the timepiece varies according to the nominal positioning of the hairspring blade relative to the stud.

[0047] The solid curve N, for its part, shows a function with an optimized isochronism slope, representative of the operation of a balance wheel and hairspring assembly equipped with a stud according to the invention, with a hairspring whose terminal curve is precisely located thanks to the first and second bearing surfaces of the stud. Such a configuration makes it possible, in particular, to obtain in practice the expected isochronism slope and the desired balance spring balance of the timepiece in which the balance wheel and hairspring are incorporated.

[0048] A method for making a ferrule is described in more detail below with reference to figures 7 to 11 .

[0049] The ferrule includes a first portion 10' intended to be welded to a spiral spring 2, in particular by laser welding, at the inner end 2b of the spiral spring as shown in the figure 8The ferrule also includes a second portion 100', in the form of a central opening 100', which is intended, for example, to be driven against a balance shaft axis 5 as shown on the figures 8 to 11 The first and second sections can be made in one piece. Alternatively, the first and second sections can be made of different materials and mounted one on top of the other.

[0050] Like the eye pin 1, the portion 10' has a first groove 10a' to define two bearing surfaces 10b', 10c' for a portion of the blade at the inner end of the spiral spring 2. Thus, the first portion 10' comprises a first bearing surface 10b' and a second bearing surface 10c' separated by a groove 10a'. Each bearing surface is designed to contact the spiral spring. In the illustrated embodiment, the groove extends along the height h of the spiral spring, preferably over a height H10' greater than that of the spiral spring. The groove 10a' separates or distinguishes the first and second bearing surfaces 10b', 10c'. The groove 10a' is advantageously oriented substantially along the height H10' of the portion 10 of the eye pin 1.This design prevents any heat conduction during the welding of the spiral blade to each of the first and second bearing surfaces 10b', 10c', and avoids interference between two thermally affected areas of the spiral spring during welding. This design reduces the energy input required for welding and thus best preserves the integrity of the mechanical properties of the spiral spring alloy. The groove can also serve as a visual guide for precisely positioning the weld points on the periphery of the ferrule.

[0051] Alternatively, as previously described, the groove can be oriented perpendicular to the height h of the spiral spring. Alternatively still, the groove can be oriented in another direction.

[0052] In an embodiment not shown, the first bearing surface may have, at one of its ends, a first raised or bulged shape. This first shape provides a positioning stop for the spiral spring. The spiral spring blade, in contact with the first surface, can be moved until it contacts this first shape, thus precisely positioning the spiral spring relative to the ferrule along the ferrule's height. The first shape extends, for example, perpendicularly or substantially perpendicularly to the first surface 10b', so as to form a stop. Advantageously, the first bearing surface 10b' may have, at its other end, a second raised or bulged shape. This second shape provides a positioning stop for the spiral spring.The second conformation extends, for example, perpendicularly or substantially perpendicularly to the first surface 10b', so as to form a stop.

[0053] Similarly, the second bearing surface 10c' may have, at one of its ends, a third raised or bulged shape. This third shape provides a positioning stop for the spiral spring. The spiral spring blade, in contact with the second surface, can be moved until it contacts this third shape, thus precisely positioning the spiral spring relative to the ferrule along the ferrule's height. The third shape extends, for example, perpendicularly or substantially perpendicularly to the second surface 10c', forming a stop. Advantageously, the second bearing surface 10c' may also have, at its other end, a fourth raised or bulged shape. This fourth shape provides a positioning stop for the spiral spring.The fourth conformation extends, for example, perpendicularly or substantially perpendicularly to the second surface 10c', so as to form a stop.

[0054] The set of positioning configurations described above allows for precise positioning of the spiral spring blade relative to the pin and, consequently, precise embedding of the spiral spring after welding it to the ferrule. Welding can be performed using two tack welds s1', s2', which are respectively made at each of the bearing surfaces 10b', 10c' or at the edge of each of the bearing surfaces 10b', 10c'. Preferably, a third and fourth tack weld s3', s4' are made respectively at each of the bearing surfaces 10b', 10c', or at the edge of each of the bearing surfaces 10b', 10c', in addition to the tack welds s1', s2', as shown in the diagram. figure 9To ensure this precise positioning, when one or two of the bearing surfaces each have two positioning configurations, they are spaced apart by a distance greater than the height h of the spring leaf. Advantageously, this vertical clearance is less than 0.04 mm, or even less than 0.03 mm. The set of positioning configurations described above can thus form a second groove oriented substantially perpendicular to the first groove, so as to serve as a support and / or guide for the spiral spring leaf.

[0055] Advantageously, the first and second bearing surfaces 10b' and 10c' are designed to perfectly match the curvature of the balance spring. To achieve this, the first and second surfaces 10b' and 10c' can form an angle α' with each other, specifically an angle a' between 150° and 179° as viewed from the axis A1 of the balance wheel or balance spring. In other words, the axis A1 lies in the obtuse dihedral angle formed by two half-planes passing through the first and second surfaces, respectively. The first and second surfaces can also be arranged perpendicularly or substantially perpendicularly to the plane P1 of the balance spring. The first and second surfaces can be flat faces. These can be flat faces tangent to the same surface, in particular to the same cylinder of revolution.The precise positioning of the balance spring relative to the ferrule also allows for chronometric improvements of the same nature as those obtained by the precise positioning of the balance spring relative to the stud.

[0056] Advantageously, the surfaces 10b', 10c' are portions of the same cylinder of revolution whose directrix is ​​the circle A with center CA, which may or may not be centered on the axis A1 of the balance wheel. In the embodiment illustrated in the Figure 10 , the center CA is not located on the axis A1 so as to minimize, or even eliminate, the displacement of the surfaces 10b', 10c' on which the spiral spring is welded during the driving of the ferrule 1' onto the axis 5.

[0057] The ferrule 1' may include arms 1A', 1B', 1C', 1D', which may or may not be deformable and may or may not have variable cross-sections, in order to optimize the force required to press the ferrule onto the balance staff and / or the torque required to hold the ferrule on the balance staff. Preferably, the contact between the ferrule and the staff is of the cylinder-to-cylinder type. The central opening 100' may be in the form of a circular bore 100' designed to fit the cylindrical periphery of the balance staff 5, so as to minimize stresses within the ferrule during the pressing operation of the ferrule onto the balance staff.

[0058] Preferably, the ferrule includes at least one peripheral portion or stop 1E', 1F', 1G', against which the inner coil of the balance spring can bear in the event of an impact, before the elastic limit of the material constituting the balance spring is exceeded. These stops are distributed angularly, regularly or irregularly, on the outer periphery of the ferrule as illustrated in the figure 11Preferably, these stops are in the form of arc segments tangent to circles E, F, and G centered at CE, CF, and CG, respectively. In the embodiment shown, circles E, F, and G have distinct diameters to best follow the geometry of the inner coil of the balance spring. The centers CE, CF, and CG coincide here and align with axis A1 or center CB of the balance wheel axis 5, and are therefore distinct from center CA. The stops 1E', 1F', and 1G' are located at distances RE, RF, and RG from axis A1, respectively, which increase in the direction of the balance spring from the inside out, from the point where the balance spring joins the ferrule.

[0059] An embodiment of a manufacturing process for an assembly 300 comprising: a spiral spring; and a pin 1; and / or a ferrule 1', is described below.

[0060] The process includes the following steps: Supply of the spiral spring as described above; Supply of the eyelet as described above and / or the ferrule as described above; Fixing of the eyelet and spiral spring and / or fixing of the ferrule and spiral spring.

[0061] Advantageously, the fixing step(s) include the following sub-steps: Positioning of the stud relative to the spiral spring and / or positioning of the ferrule relative to the spiral spring; Welding, in particular laser welding, of the stud onto the spiral spring and / or welding, in particular laser welding, of the ferrule onto the spiral spring;

[0062] Advantageously, the welding sub-step includes making at least one weld point, in particular two weld points, on each of the first and second surfaces of the stud intended to receive the spiral spring and / or making at least one weld point, in particular two weld points, on each of the first and second surfaces of the ferrule intended to receive the spiral spring.

[0063] There figure 13The graph presents a comparative analysis highlighting the advantages of an assembly produced according to the manufacturing process described above. The graph shows different situations on the x-axis and the intensity of the pull-out forces on the y-axis. Considering a reference force FA required to pull out an Nb-Zr balance spring containing approximately 15% Zr by mass from a steel stud, the Applicant's studies show that the force FB required to pull out the same Nb-Zr balance spring from the same stud made of grade 5 titanium is approximately three times the reference force FA, with the forces FA and FB applied directly to the balance spring blade in the vicinity of the stud, positioned in the plane of the balance spring, and oriented approximately towards the center of the balance spring.

[0064] If we also consider a reference force FC required to pull out an Nb-Zr balance spring comprising approximately 15% by mass of Zr from a ferrule made of steel, the Applicant's studies show that the force FD required to pull out the same Nb-Zr balance spring from the same ferrule made of grade 5 titanium is on the order of 1.1 times the reference force FC, with the forces FC and FD applied directly to the extremity of the balance spring blade at the level of the ferrule and arranged in the plane of the balance spring in a direction substantially tangent to the portion of the arc of the ferrule which receives the balance spring.

[0065] Thanks to this invention, it is possible to optimize the weld strength of a spiral spring made of a paramagnetic alloy, particularly in the event of an impact, by selecting fasteners whose portion intended to come into contact with the spiral spring is made of titanium or a titanium alloy, or tantalum or a tantalum alloy. Such a combination of materials allows for a high-quality weld thanks to the complete solubility of the solid phases, thus preventing the formation of brittle intermetallic compounds, as well as a small solidification gap, thereby limiting the risk of solidification cracks.

Claims

1. An assembly (300) comprising: - a hairspring (2); and - a fastening stud (1) for an end (2a) of a hairspring (2), the stud having a first portion (10) designed to come into contact with the hairspring (2), the first portion being formed such as to have a first surface (10b) and at least one second bearing surface (10c) with the hairspring, the first surface and the at least one second surface together forming an angle (α) between 150° and 179° considered from an axis (A1) of the hairspring (2), the stud and the hairspring being attached by welding at the level of the first and second surfaces, the first and second surfaces being discontinuous.

2. The assembly as claimed in the preceding claim, wherein the first and second bearing surfaces are separated by a slot (10a), the slot extending notably in the direction of the height (h) of the hairspring, preferably over a height (H10) greater than the height of the hairspring.

3. The assembly as claimed in one of the preceding claims, wherein each surface has, at one of the ends (101b, 102b, 101c, 102c) of same in the direction of the height (h) of the hairspring, a positioning shape (103b, 104b, 103c, 104c) extending perpendicular or substantially perpendicular to the surface (10b, 10c).

4. The assembly as claimed in one of claims 1 to 2, wherein each surface has, at two of the ends (101b, 102b, 101c, 102c) of same in the direction of the height (h) of the hairspring, respectively a first positioning shape (103b, 103c) and a second positioning shape (104b, 104c), the shapes extending perpendicular or substantially perpendicular to said surface.

5. The assembly as claimed in one of the preceding claims, wherein it includes a second portion (100) designed to come into contact with a stud support (3).

6. The assembly as claimed in one of the preceding claims, wherein the first and second surfaces (10b, 10c) are flat or cylindrical, in particular cylinders of revolution.

7. The assembly as claimed in one of the preceding claims, wherein the first and second surfaces (10b, 10c) are arranged substantially perpendicular to a plane (P1) of the hairspring (2).

8. The assembly as claimed in one of the preceding claims, wherein the first and second surfaces (10b, 10c) are arranged substantially perpendicular to a plane (P1) of the helical spring and / or are curved to form portions of a single cylinder of revolution or are made tangential to a single cylinder of revolution.

9. The assembly as claimed in one of the preceding claims, wherein at least one of the first and second surfaces (10b, 10c) forms a non-zero angle with a plane that is parallel and orthoradial to the axis of the hairspring.

10. A manufacturing method for an assembly (300) as claimed in one of claims 1 to 9, the method including the following steps: - Provision of the stud, - Provision of the hairspring, - Fastening of the stud to the hairspring at the level of the first and second surfaces.

11. The manufacturing method as claimed in the preceding claim, wherein the fastening step is performed by laser welding.

12. A clockwork oscillator (400) or clockwork movement (500) or timepiece (600) including: - an assembly (300) as claimed in one of claims 1 to 9, and / or an assembly (300) obtained by carrying out the method as claimed in either of claims 10 and 11.

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