EP3283926A1 - Magnetic antishock system for a timepiece arbor - Google Patents

Abstract

Watch subassembly (200), including an arbor (10) comprising a magnetised or charged surface (16) pivoting in a housing (14; 15), and a polar weight (11; 12; 31; 32) subjecting this surface to a magnetic or electrostatic field about an axis (DA), a polar weight (11; 12; 31; 32) interacting axially with this surface to absorb a shock and then subsequently return the arbor (10) to its operating position, and creating, in proximity to the surface, a magnetic or electrostatic field that either attracts the arbor (10) radially toward a wall of the housing (14; 15) or varies along the axis (DA) and applies to the arbor (10) a resistive force resulting from the interaction between a polar weight (11; 12; 31; 32) and the surface.

Description

 Magnetic shock absorber for a timepiece tree Field of the invention

 The invention relates to a watch-making subassembly for a watch, comprising a main structure and a movable shaft pivoting about a pivot axis in at least one housing of said main structure, said shaft comprising at least one surface in a magnetic material. or ferromagnetic, or respectively in an electrified material or electrostatic conductor, and said main structure comprising at least one pole mass arranged to create, near at least one said surface, a magnetic field, or respectively an electrostatic field, for a maintenance axial and radial of said shaft.

 The invention also relates to a movement comprising at least one such subset.

 The invention also relates to a watch comprising at least one such subassembly.

 The invention relates to the field of watch movements comprising mechanical components pivoting.

Background of the invention

 In watchmaking, and more particularly for watches, a mechanical technology is generally used for maintaining a component, in particular a shaft, in a particular position. It can be an abutment with an elastic system, especially when a certain freedom of movement is necessary for the case of a shock. For example, a spring holds a shaft in abutment.

 Maintaining by a pre-stressed spring is not stable over time: such a spring, which must work with variations of stress due to the shocks to the watch, is subjected to fatigue and wear, same as each component that is subjected to percussive efforts in abutment.

In addition, the manufacture of such a spring is difficult to reproduce. The set of tolerances can, again, provoke a great dispersion as to the value of the pre-stress effort. As a result, the performances are not stable over time, and the shockproof effect also degrades during the life of the watch.

 In summary, the main problems encountered with mechanical elastic holding systems are component wear caused by repeated mechanical stresses, and the need for realizations with tight, and therefore expensive, tolerances.

 It remains difficult to ensure the axial retention of a watch tree, with an unalterable shockproof mechanism.

 The application EP 2450 758 in the name of MONTRES BREGUET SA describes a method of orienting a watch component magnetically or magnetically permeable material having two ends, where on both sides are created two magnetic fields each attracting the component on a polar mass, with an imbalance of intensity of the magnetic fields around the component to create a differential of forces on the latter and to press one of the ends on a contact surface of one of the masses, and maintain the other end to distance from the other polar mass. This application also describes an electrostatic variant on the same principle. The application also relates to a magnetic pivot (or an electrostatic variant) comprising such a clock component, comprising a guide device with, at a gap distance greater than the center distance between the ends, surfaces of two polar masses arranged to be attracted. each by a magnetic field emitted by one of the ends, or each to generate a magnetic field attracting one of the ends, so that the magnetic forces exerted at both ends are of different intensity, to attract one of the ends in contact with a only polar surfaces.

The application EP 2450 759 in the name of WATCHES BREGUET SA describes a magnetic (or electrostatic) shockproof device for the protection of a watch component pivotally mounted between a first and a second ends. It comprises, on either side of these ends, on the one hand pivoting guide means or means of attraction of the first end held in abutment on a first polar mass, and on the other hand, in the vicinity a second polar mass of means for pivotally guiding the second end or means for attracting the second end towards the second pole mass, and the pivoting guide means or means for attracting the first end on the one hand, and the pivoting guide means or attraction means of the second end on the other hand, are movable along a given direction between stops.

 Document FR1314364 in the name of HELD describes a combination of magnets for magnetic suspension of contactless clock pivots, with the combination of an annular disk magnet pierced right through the center. In a first variant, this magnet is magnetized radially, with one pole on the internal generators of the hole, the other pole on the external generators. In a second variant, this magnet is axially magnetized, the two polar areas being distributed over the two circular flat surfaces of the disk, the axis of the magnetically held and guided moving element passing through the center of the hole of the annular magnet. axis being constituted by a thin-walled non-magnetic tube containing a hyper-coercive material, magnetized in one piece with two poles of opposite name at the two ends, or in two segments separated by an interval, the ends opposite the two segments housed in the protective tube having poles of the same name, in mounting with fixed magnet-disc, with radial polar axes and poles of opposite name in mounting with axially magnetized disk, the gap separating the two segments forming the core of the tubular axis being of the same order as the thickness of the disk considered and placed inside the central hole of the latter, so that the terminal ends of e the axial filiform magnet protrude slightly inside the hole, the two flat, circular surfaces delimiting the height of the cylinder or magnetic disc.

Summary of the invention

 The invention proposes to define an architecture for maintaining a position in a position of a clockwork tree, which is capable of ensuring a stable shock effect over time, and which is reproducible.

 For this purpose, the invention relates to a horological watch subassembly according to claim 1.

 The invention also relates to a movement comprising at least one such subset.

The invention also relates to a watch comprising at least one such subassembly. Brief description of the drawings

 Other features and advantages of the invention will appear on reading the detailed description which follows, with reference to the appended drawings, in which:

FIG. 1 is a diagrammatic perspective view of a timepiece subassembly according to the invention comprising a shaft which is held radially, by magnetic attraction or repulsion, in a first bore by a first pole mass forming a substantially tubular sector, the axis of this shaft is maintained along a pivot axis substantially corresponding to the axis of the first bore; this shaft is held axially by a second polar front mass, in a chamber here defined by a second bore that comprises a substantially tubular limiting sleeve; this subassembly is represented without any positioning stops;

 - Figure 2 shows schematically and in section, the subset of Figure 1;

 - Figure 3 shows schematically and in top view, the subset of Figure 1;

 - Figures 4 and 5 show, respectively in section and in plan view, another similar subset, wherein the first pole mass is of revolution around the shaft;

 FIG. 6 is a diagrammatic sectional view of a cladding or movement subassembly according to the invention, in a first variant comprising a radial mechanical guide, and at least one magnet which provides the axial holding of a shaft in an axial direction; this subassembly comprises a structure with a lower wing comprising a magnet at the bottom of a housing; this housing receives a shaft, which is subjected to a magnetic attraction force in a field direction parallel to the axial direction; the structure comprises an upper wing, limiting the movement of the insert and forming a safety stop over the shaft;

- Figure 7 shows, similarly to Figure 1, a reverse configuration, where the safety stop is below the shaft, and where a tribological surface is introduced on the stop;

FIG. 8 schematically shows in section and in section a magnet and a magnetic part in attraction, constituting a structure and a shaft comprising each, at their respective contact surfaces, a tribological or anti-wear layer;

 FIG. 9 schematically shows in section a structure with a magnetic housing receiving a magnet in the form of a nail with a head, which comes to press a spacer forming part of a tree and which is held prisoner and pressed onto the structure by this magnet, pinched between the head of the magnet and the fixed element;

- Figure 10 shows, schematically, partially and in section along its axis, a shaft having a plurality of magnets, whose polarity is schematized by hatching or by a crisscrossing, and which is movable between other fixed magnets that includes a structure in which this tree is movable;

 - Figure 1 1 shows another magnet-carrying shaft configuration between other fixed magnets of the structure;

 FIG. 12 schematically shows, partially and in section, a structure in the form of a fixed line in a z-direction, comprising an alternation of parts, on the one hand, paramagnetic or ferromagnetic, and on the other hand diamagnetic, schematized respectively; by a hatching and a crisscrossing, along which structure, which is fixed, is alignable a cylindrical shaft having a permanent magnet, not shown;

 FIG. 13 is a diagrammatic front view of a watch comprising a movement comprising such a subassembly;

 FIG. 14 is a diagrammatic fragmentary view, in section through the axis of pivoting of its shaft, of a watchmaking subassembly according to the invention, comprising a pivotally movable shaft in a structure, where shaft generates an axial field at a lower end, and a substantially conical field around the pivot axis with a first intensity in the direction of the pivot axis, and wherein the structure in which the shaft is movable comprises a succession zones generating conical type fields, tending to oppose the fields generated by the shaft, and which have, since a service position of the shaft illustrated in FIG. 14A, increasing intensities as and when the bringing together of the lower part of the race of the tree; each of these zones of field of the structure constitutes a virtual notch, which slows down the tree in its descending run:

FIG. 14B shows the subassembly of FIG. 14A after an impact or a strong acceleration, the shaft starting a stroke towards a lower end of stroke not shown, and in a position where this tree has just crossed a first field barrier symbolized by simple arrows, substantially symmetrical and opposite to the conical field that includes the tree itself, and where the tree arrives on a second barrier of field, axial intensity greater than that of the first barrier, and symbolized by double arrows,

 - Figure 14C shows the same subset in the case where the kinetic energy printed on the tree is important and allows it to cross this second field barrier, and where the tree arrives on a third field barrier, d axial intensity greater than that of the second barrier, and symbolized by triple arrows, and which, in this example, suffices to stop the axial stroke of this shaft,

FIG. 14D shows the subsequent raising of the shaft towards its operating position of FIG. 14A under the action of the repulsive fields to which it is subjected;

 FIG. 15 illustrates, in the same way as FIG. 14, a similar arrangement, but in which the shaft generates only an axial end field, and where the third conical barrier at the lower end of the race is replaced by an axial field barrier of similar intensity, and a sequence of descent and ascent of the shaft on its axis which is similar to that of Figure 14;

 FIG. 16 illustrates a structure comprising a housing in which a shaft is movable, with at the lower and upper ends of the shaft and the housing a symmetrical arrangement corresponding to the variant of FIG. 15;

 FIG. 16A illustrates, in a manner similar to FIG. 16, a variant in which the fields generate attraction forces instead of repulsion efforts;

 FIG. 16B illustrates, in a manner similar to FIG. 16, a variant in which the radial fields generate attraction forces instead of repulsive forces, whereas the axial fields of the structure generate repulsion forces;

FIG. 17 illustrates, in perspective in view 17A and in top view in view 17B, a subassembly according to FIG. 16, including a lateral cut parallel to the axis of pivoting of the shaft and allowing its insertion and its extraction;

FIG. 18A is a schematic perspective view of a mechanism exploiting the system of FIG. 12, with a shaft having in the middle part a dark permanent magnet placed close to the structure in the form of a line, here in the form of a shell concave with alternating diamagnetic and paramagnetic / ferromagnetic zones; Fig. 18B is a sectional view of the whole of Fig. 18A, and Fig. 18C illustrates the polarities generated by the presence of permanent magnet, fixed on the tree, and by the magnetic properties of the zones on the hull; the shaft provided with a permanent magnet then undergoes a force similar to the versions of Figures 10 to 12, but generated by diamagnetic and paramagnetic / ferromagnetic zones;

- Figures 19A and 19B are similar to Figures 18B and 18C, but for a system operating a maintenance in mechanical contact, the portion shown in crosspieces being fixed;

 FIG. 20 is a curve with the magnetic force exerted between two cylindrical magnets of the same power and diameter as a function of the ratio of their relative heights on the abscissa, the value 0.5 corresponding to the case where they are of the same height;

 FIG. 21 is a curve with the magnetic force exerted between a magnet and a cylindrical ferromagnetic part of the same diameter as a function of the ratio of their relative heights on the abscissa, the value 0.25 corresponding to a ferromagnetic part three times smaller than the magnet;

 FIG. 22 is a diagrammatic partial view in section of a clockwork movement comprising a subassembly according to the invention, with a shaft drawn axially by a polar mass, and whose end is in friction on the front part of it.

Detailed Description of the Preferred Embodiments

 The effects of mechanical stresses in a component depend on a large number of parameters whose tolerance range is often wide. The consequences of friction and wear are especially difficult to control because they strongly depend on the surface conditions and physical properties of the materials used.

These properties themselves depend on the alloys used and the processes used, in particular heat treatment, surface treatment, and ion implantation. The combination of the tolerances specific to the different parameters of the processes and materials prevents to know and to control precisely these physical properties. And reproducibility is not assured, because of these tolerances. Or the reduction of tolerance ranges, which provides a better reproducibility of phenomena, leads to costs too high for mass production. The theory governing magnetic interactions is, for its part, fully described by Maxwell's equations, and the remaining unknowns come from the magnetic materials used, which are better and better mastered, and from the difficulty of solving these equations analytically and numerically. with the smallest approximations possible. Nevertheless, from a macroscopic point of view these inaccuracies are sufficiently weak to make the magnetic systems intrinsically reliable.

 The invention proposes a weathering shaft support, of the shockproof type, in an unalterable manner, under the effect of a magnetic and / or electrostatic field.

 It is more particularly described with nonlimiting examples of a magnetic application. The invention can also be implemented with the use of electrostatic fields, particularly through the use of electrets. Or by combining magnetic fields and electrostatic fields.

 Here, the term "shaft" means any watch component arranged to pivot about a theoretical pivot axis. The invention is described hereinafter essentially for the tree parts of such a component, or mobile, or the like. For example, in the case of a pendulum we will focus more particularly on the ends of the tree part of this pendulum. The invention is illustrated in a simplified manner with a revolution shaft, comprising one or more cylindrical bearing surfaces. But this illustration is not limiting, the invention can be applied to any type of component, such as anchor, escape wheel, wheel, pinion, or other.

 It is proposed in these examples to use magnetic forces to construct an axis holding system, exploiting the forces induced on a piece of magnetized material immersed in a magnetic field. This force is given (for the interaction between a magnet and a magnetic part) by the following law:

 F = (M-V) B (1)

where M is the magnetization of the material and B is the external magnetic field, all the quantities in (1) being vectors.

The principle is to position one or more magnets on a fixed part, and to exploit the magnetic force that undergoes a ferromagnetic component (attraction), diamagnetic (repulsion) or paramagnetic (attraction) which must be fixed. This component therefore undergoes a force of attraction or repulsion, which can be used to hold it in place.

 A first variant, in Figures 1 to 3, is to use the magnetic force to constrain in three directions a shaft, for example by keeping it in contact in a triangle which positions it (positioning stops). The contact can also be made directly on the permanent magnets.

 A second variant, in FIG. 4, with a radial mechanical guide and a magnet that provides axial retention, concerns the cases where the magnetic force is used to constrain a shaft in one or both of the three directions, whereas a mechanical guidance is used to limit its movement in other directions. Typically, radial guidance can be performed via a chimney while the shaft is held axially by a magnet.

 The number of magnets used can of course change from one variant to another. One can imagine, for example, a construction which uses a ring of several magnets instead of a simple magnet for the z-axial holding in FIGS. 1 to 4. This has the advantage of averaging the defects of the components, and of exerting effort, especially force, on a higher radius.

 In this magnetic application described below, a holding system is constructed, exploiting the forces in the broad sense, that is to say, forces or torques, induced on a piece of magnetized material or ferromagnetic material immersed in a magnetic field. . This effort depends on the magnetization of the material, or its magnetic permeability, and the intensity of the local magnetic field. In a particular embodiment, one or more magnets are positioned on a fixed part called a structure, or / and on the shaft. This shaft undergoes (or generates, in the case where it is itself magnetized and cooperates with a magnetized magnetic or non-magnetized environment) an attraction or repulsion force that can be used to hold it in place.

 For lightweight elements, and if the space allows the presence of one or more magnets capable of generating a sufficient magnetic field, the magnetic force alone can be sufficient to retain an element during shocks.

Nevertheless, in most cases this force is too weak. When the magnetic force is too weak to withstand a shock, it is possible to introduce a safety stop limiting the excessive displacement, as visible on the FIGS. 6 and 7, which represent two type configurations of FIG. 4, with a safety abutment, once above the component and once beneath it, and potential contact zones referenced 5. The magnetic retention is therefore used to counteract low shocks, with a limiting amplitude from which the component peels off to abut. This mode of operation has the advantages of the springs, while causing a lower shock when returning to position. Indeed, the magnetic system, as opposed to the spring, exerts a force that decreases with the distance of the part relative to its stance. The energy stored during an accidental shock (which is released when the component returns to position) is therefore lower.

 The force can also be generated by two magnets. FIGS. 20 and 21 show the magnetic force Fm, in Newton, that can be generated by a system with two magnetic bodies, respectively with two magnets in FIG. 20, or with a magnet and a ferromagnetic part in FIG. 21, as a function of the ratio h1 / h2 of the relative size of these two bodies.

 In a further variant, the magnetic system not only has a role of maintenance, but also facilitates the function of setting / replacing, as visible in Figures 10 and 1 1. In the first case of Figure 10, an additional force must be applied to overcome the repulsion of the magnets, and once the system is in place, it is maintained in the axial direction z; such a system becomes particularly interesting if it is combined with the introduction of stones, or any other tribological surface, to minimize the friction of the radial contact. The second case of FIG. 11 is a magnetic re-centering system, where the shaft, including permanent magnets, is held against a line-shaped structure composed of attractive parts and repulsive parts. These parts can also be made of permanent magnets. The radial strength of this system is magnetic via the attractive parts (with the possibilities of variants presented above); the component is refocused magnetically after each shock. This system is easily adaptable for a degree of angular freedom.

 The line-like structure of Fig. 12 with attractive and repulsive regions can also be directly on the shaft with a permanent magnet on the fixed part of the movement.

Different geometrical configurations are thus usable. It is thus possible to use the magnetic force to constrain a covering element or movement in the three directions, for example by keeping it in contact in a female trihedron which positions it, and which also constitutes a set of positioning stops. The magnetic elements may be recessed with respect to the contact surfaces. Contact can also be made directly on surfaces of magnetic components.

 One variant concerns the case where the magnetic force is used to constrain an element in one or both of the three directions, while a mechanical guidance is used to limit its displacement in the other directions.

 Thus, the invention is more specifically described with regard to the axial damping of a shaft. The pivoting of the shaft may be traditional, by guidance in a stone or a bearing, or be magnetic type, or other, especially combined.

 For each of these variants, when the magnetic force is too weak to withstand a shock, it is possible to introduce a safety stop, so as to limit the displacement of the shaft and avoid too much travel. Magnetic hold is therefore used to counteract low shocks, with an amplitude from which the magnetically maintained shaft peels off to a safety mechanical stop. This mode of operation has the advantages of the springs, while causing a lower shock when returning to position. Indeed, the magnetic system, as opposed to the spring system, exerts a force that decreases with the distance of the shaft relative to its service position, held. The energy stored during an accidental shock, which is released when the element returns to position, is therefore lower.

 In an advantageous embodiment of the invention, the cooperation of the magnetic and / or electrostatic fields present at the level of the structure and / or the shaft is sequenced, and comprises electromagnetic barriers which depend on the relative position of the tree and structure, and the passage of each consumes all or part of the kinetic energy of the tree during an impact.

 The relative force can be generated by two magnets, or by a magnet near a ferromagnetic (attraction), diamagnetic (repulsion) or paramagnetic (attraction) part.

The tree to be held in place can itself be ferromagnetic, diamagnetic or paramagnetic and be located near a magnet, or comprise itself one or more magnets or magnetized zones, or respectively electrified.

 In the case where the effort is caused by two magnets, they can work in attraction or repulsion; work in attraction theoretically causes a slower aging of the magnetic system. The repulsion mode is, however, easier to implement for end-of-shaft damping, and this non-limiting mode is described in the examples illustrated.

 The damping characteristics according to the invention, by magnetic or electrostatic means, are good for shocks of small or medium magnitude. If it is conceivable to use this technology for the complete absorption of the exceptional kinetic energy of the tree during an impact, it is clear that it is then at the expense of congestion. Also the invention is preferably combined with a conventional mechanical stop, which may be a stopper, or a bearing surface of a spring which is not in contact with the shaft during low or medium magnitude shocks . Preferably any magnet surface is protected, because of its fragility, by another surface that comprises, as the case, the shaft, or the structural element concerned. Thus, the contact between antagonistic components, such as a main structure 100 and a shaft 10, may be a contact of a portion of the shaft to be held against a positioning stop, which is not necessarily magnetic.

 In a preferred application of the invention, the magnetic or electrostatic means, which are implemented to constitute an axial shock of the shaft, are also used to ensure an axial retention of the shaft in its operating position. It is understood that the contacts are completely avoided only in repulsion configurations as in FIG. 16. In most other cases, even while working in repulsion, a contact on the shaft is inevitable. The circumferential friction dissipates more energy than the friction on the front part.

The invention is particularly suitable for maintaining contact with the shaft, both axially and radially. Because the configuration with a remote maintenance of the shaft, axial or / and radial, advantageous in terms of friction, can not always be implemented. Note in this connection that a magnetic or electrostatic cooperation between the shaft and receiving structure is not necessarily only axial.

 Advantageously, this cooperation provides a radial hold, to permanently tend to align the shaft 10 on its theoretical pivot axis DA. Therefore, even if the traditional pivoting guidance of the shaft 10 is not perfect, this guidance is optimized by the influence of magnetic or electrostatic fields that tend to realign the shaft 10 permanently along its axis DA.

 In Figures 1 to 4, the contact is not shown; this contact may be directly from the magnet against the shaft (or the fixed magnet against the magnet of the part to be kept in contact if appropriate), as in Figure 8 or a part of the component to maintain against a positioning stop (not necessarily magnetic) as in Figure 9. The surface against which the contact is maintained can be adapted to optimize its tribological and mechanical properties.

 In an alternative conventional guiding of the shaft in the structure, via contact surfaces, these surfaces can undergo adaptation optimization of their tribological properties, and / or mechanical, and / or anti-wear. A surface layer, as visible in FIG. 8, which can also be produced in the variant of FIG. 9, or others, may for example be corundum, diamond or a protective coating. This superficial layer may also be made of a material that combines special tribological and magnetic properties, such as tungsten carbide, especially with a cobalt binder.

 For lightweight elements, and if the space allows the presence of one or more magnets capable of generating a sufficient magnetic field, the magnetic force alone can be sufficient to retain an element during shocks.

Different geometric configurations are usable. In the illustrated examples, the magnetic forces (or / and couples) are used to construct a shaft maintenance system, exploiting the forces induced on a piece of magnetic material immersed in a magnetic field. To do this, one or more magnets is positioned preferably on a fixed part, and the magnetic force experienced by a ferromagnetic component (attraction) is exploited. diamagnetic (repulsion) or paramagnetic (attraction) which must be fixed. This component will therefore undergo an attraction or repulsion effort that can be used to hold it in place. Reverse relative positioning is also possible.

 A variant represented in FIGS. 1 to 3 consists in using a magnetic force to constrain a shaft 10 in the three directions, for example by keeping it in a trihedron which positions it, or in contact by positioning stops not shown, or / and by magnetic interaction with permanent magnets. For example, any shaft 10 cooperates with a first structure 11 which radially surrounds a first upper bearing surface 16 of the shaft, and with a second structure 12 in its axial alignment along the pivot axis DA. In a particular case, this first structure 1 1 and this second structure 12 are magnets. A third structure 13 has a bore 15 which limits the radial movement of a lower bearing surface 17 of the shaft 10.

 Another variant, represented in FIGS. 4 and 5, illustrates the cases where the magnetic force is used to constrain a shaft 10 in one or both of the three directions, here in the axial direction corresponding to the pivot axis DA, while mechanical guidance is used to limit the displacement of the shaft 10 in the other directions. Typically, the radial guidance can be carried out via a chimney, at a bore 14 of a first structure 11, while the shaft 10 is held axially by a magnet which comprises a second structure 12.

 The number of magnets used can of course change from one variant to another. A construction comprising a ring of several magnets instead of a single magnet for axial retention in the axial direction, in the examples of FIGS. 1 to 5, thus has the advantage of averaging the defects of the components, and of exerting the 'effort on a higher radius. This can be an advantage if the mechanism is designed to exploit eddy current dissipation to increase the frictional capacity of a magnetic equivalent of a friction spring.

The preferential solution, but not limiting, thus uses a magnetic attraction force, or between two magnets, or between a magnet and a magnetically conductive part, in particular ferromagnetic. It allows a better stability and a better control in position of the parts. It is understood that equation (1) is valid only for determining the force between a magnet and a magnetic part (it is not valid for determining the force between two magnets), and in most cases the magnetic piece is ferromagnetic, and will therefore be aligned in accordance with the magnet: in this case, the force is attractive. Only in the case where the magnetic piece is diamagnetic, there is a repulsive force between the magnet and the component, but this force is ten to one hundred times weaker than that which can be obtained in attraction.

 The solutions illustrated in FIGS. 1 to 4 use only the force of attraction, the direction of the forces tends to bring the parts together, the force is negative, either in the ferromagnetic magnet-piece variant, or in the variant with two magnets.

 Only Figure 5 corresponds to a solution where the attraction and repulsion forces are combined to stabilize the position of the component.

 The repulsive solutions make it possible to dissipate part or all of the energy of the shocks by magnetic repulsion rather than by mechanical shock.

For lightweight trees, and if the size allows to introduce a sufficient number of magnets, the magnetic force alone can be enough to hold a tree during shocks. Nevertheless, in most cases this effort, limited by congestion constraints, is too small. When the magnetic force is too weak to withstand a shock, it is possible, as shown in Figure 6 or 7, to introduce a safety stop limiting the excessive displacement. These two configurations show a safety stop, once above the component in FIG. 6, and once below in FIG. 7. Magnetic retention is therefore preferentially used to counteract weak impacts, with a limiting amplitude, from from which the component is released from the magnetic influence, to go into mechanical stop under the effect of the rest of its kinetic energy. This mode of operation has the advantages of spring-loaded, while causing a lower shock when returning to the normal operating position. Indeed, the magnetic system, as opposed to the spring, exerts a force that decreases with the distance of the shaft relative to its holding position. The energy stored during an accidental shock, which is released when the component returns to position, is therefore lower. In Figures 1 to 5, the contact is not shown. This contact may be a direct contact of the magnet with the shaft, as in FIG. 8, or a portion of the shaft to be held against a positioning stop (not necessarily magnetic) as in FIG. 9. The surface against which contact is maintained can be adapted to optimize its tribological and mechanical properties. The red surface may for example be corundum, diamond, sapphire or a protective coating. The surface can also be a material combining interesting tribological and magnetic properties, such as tungsten carbide with a cobalt binder.

 In another variant, the magnetic system has this role of maintenance, and also facilitates the function of setting / replacing, as shown in Figures 10 to 12.

 In the first case of Figures 10 and 1 1, during the axial introduction of the shaft into a bore of the structure, additional effort must be applied to overcome the repulsion of the magnets, but once the system is in place it is maintained in the axial direction DA. Such a system becomes particularly interesting if it is combined with the introduction of stones (or any other tribological surface) to minimize the friction of the radial contact, in the case where the friction is not exploited.

 The second case of Figure 12 is a magnetic centering system where the shaft 10 has permanent magnets, and is held against a line-shaped structure composed of attractive portions and repulsive portions. These parts can also be made of permanent magnets. The radial strength of this system is magnetic via the attractive parts, with the possibilities of variants presented above; the shaft is refocused magnetically after each shock. This system is easily adaptable for a degree of angular freedom. Such a line-shaped structure with attractive and repulsive regions can also be directly on the shaft 10, with a permanent magnet on the structure, linked to a fixed part of the clockwork movement.

FIGS. 18A, 18B, 18C show a mechanism exploiting the system of FIG. 12. FIGS. 18A and 18B show a shaft having a permanent magnet placed close to the line-shaped structure, here in the form of a shell (not necessarily of revolution) which comprises an alternation of diamagnetic and paramagnetic / ferromagnetic zones. Figure 18C illustrates the polarities generated by the presence of the permanent magnet (fixed on the tree) and by the magnetic properties of the zones on the hull. The shaft provided with a permanent magnet is then subjected to a force similar to the versions of FIGS. 10 to 12, but this force is here generated by diamagnetic and paramagnetic / ferromagnetic zones.

 Figures 19A and 19C are similar to Figures 18B and 18C, but for a system operating a maintenance in mechanical contact, the part designed in crosspieces being fixed.

 Returning to FIG. 10, the magnets of one of the two components (shaft or chimney) are preferably of revolution to ensure correct operation in rotation of the shaft. As for the shockproof function, the response of the system is not isotropic, if the magnets are not revolution. This is not necessarily embarrassing, since it is only a transitional regime, and therefore we can consider different configurations:

 the magnets of the tree are of revolution (and not those of the chimney) whereas the direction where the anti-shock function is maximum is fixed on the movement; this direction may correspond, for example, to a direction that receives statistically more shocks;

 - the magnets of the chimney are of revolution (and not those of the tree) then the direction where the anti-shock function is maximum is fixed on the tree; this direction may correspond to a direction where the radial position of the shaft must be better constrained than the other (for example because of the presence of a component fixed on the shaft which is not symmetrical of revolution and which would collide with another component of the movement);

 one of the two configurations above, but where the magnets which are not of revolution are not located either side; thus maintaining a mechanical contact on one side ensures the radial positioning of the shaft.

 These solutions allow more axial positioning (with mechanical guidance for the radial portion) than radial, because they work in attraction. This property makes them unstable if used for radial centering.

The variants of FIGS. 14 to 17 are provided for radial recentering by repulsion, with axial positioning abutting by force magnetic. The axial magnetic attraction variant end, not drawn, is particularly interesting.

 The variant operating in magnetic attraction has the disadvantage that the radial centering is not precise; the shaft is in mechanical contact on one of the walls of the chimney, which wall may vary during the function; but this variant also makes it possible to axially press the shaft against a stop with a restoring force depending on the position of the shaft in its chimney. An alternative with magnets that are not of revolution, similar to Figure 1, allows to press the shaft radially always on the same face, and the position of the shaft is then less variable.

 Another variant is to add a frontal magnet on the fixed structure, so as to help the axial resistance of the shaft at one end.

 Another variant, with a decreasing force instead of increasing with the displacement of the shaft in the chimney, makes it possible to obtain a strong holding force, and a contribution of the magnetic force decreasing with more amplitude shocks. important (where a stop takes over).

 It is possible to imagine different types of magnetic potential profiles, and in particular a staircase variant, in which more and more energy is absorbed during the displacement of the shaft towards its abutment. Another variant has real barriers, which technically only temporarily absorb the energy, since the latter is returned as soon as the tree leaves the zone of the barrier.

 If the variant shown in Figure 14 relates to a structure in which the shaft is movable, which comprises a succession of zones generating conical type fields, tending to oppose the fields generated by the tree, and which have, from a service position of the tree of increasing intensities as the approximation of the lower part of the race of the tree, it is understood that other variants may relate to:

 a succession of fields generating fields that tend to align with the fields generated by the tree;

 - or / and fields with decreasing intensities when approaching the lower part of the race of the tree.

The configuration where the magnetic force depends on the position of the shaft in the chimney (increasing in intensity during severe shocks) is advantageous. In this variant we can still create a dependency of the magnetic force, similarly to a mechanical spring (increasing with the spacing of the shaft from its equilibrium position).

 FIG. 22 illustrates the case of a shaft drawn axially by a polar mass, and whose end is in friction on the front part thereof

 The lateral support of Figures 1 to 3 is selected in part, to allow a maintenance in mechanical contact, and thus exploit the concept of anti-shock. For shocks of low amplitude, the shaft, typically a balance shaft, does not leave its position (maintained in a preferred angular direction) and comes off only from a certain threshold. The disadvantage of the lateral version lies in the increased friction (on the radius of the shaft and not on a reduced radius of friction). These friction can nevertheless be exploited to dissipate energy, typically to dampen the floating of a needle.

 Naturally, if on the examples the shaft and the magnet are illustrated in attraction, it is quite possible to create the same system in repulsion, which then establishes a contact on the opposite side.

 In order to protect the outside of the watch, in particular the user and certain sensitive devices, against the magnetic fields of such a system, and in order to increase the efficiency of the holding system, it is possible, and advantageous, to to introduce a ferromagnetic shield or to use the caseband as such.

 More particularly, the invention relates to a watch 200 sub-assembly for a watch, comprising a main structure 100 and a shaft 10. This shaft 10 is pivotally movable about a pivot axis DA, in at least one housing 14, 15 of this main structure 100.

 This shaft 10 comprises at least one surface 16, 18, 21, 22, which is made of a magnetic material or magnetic conductor, or respectively in an electrified material or electrostatic conductor. Here is called "magnetic conductor" a ferromagnetic material or diamagnetic or paramagnetic.

 To cooperate with this shaft 10, the main structure 100 comprising at least one polar mass January 1, 12, 31, 32, which is arranged to create, near at least one such surface 16, 18, 21, 22, to less a magnetic field, or respectively an electrostatic field, for the axial and / or radial retention of the shaft 10 with respect to the pivot axis DA.

In the case of an axial retention of the shaft 10, this field is substantially of revolution about the pivot axis DA. In a variant, the main structure 100 comprises at least one polar mass 1 1, 12, 31, 32, arranged to create, close to at least one such surface 16, 18, 21, 22, in addition to the field intended for the axial retention of the shaft 10, at least one magnetic field, or respectively an electrostatic field, for a radial holding of this shaft 10.

 More particularly, this field provides both axial and radial retention of the shaft 10.

 According to the invention, at least one such polar mass 1 1, 12, 31, 32 is arranged to cooperate in axial attraction or repulsion and / or radial, along the pivot axis DA, with at least one such surface 16, 18, 21, 22, to absorb a shock and return the shaft 10 to the service position after the cessation of this shock.

 According to the invention, at least one polar mass 1 1, 12, 31, 32 is arranged to create, close to at least one such surface 16, 18, 21, 22, at least one such magnetic field, or respectively electrostatic, which:

or else tends to attract the shaft 10 radially toward a wall of the housing 14, 15; - or varies along the pivot axis DA and is arranged to apply to the shaft 10 a resistive force resulting from the cooperation in attraction or repulsion between at least one polar mass 1 1, 12, 31, 32, and at least one surface 16, 18,

21, 22.

 More particularly, at least one such polar mass January 1, 12, 31, 32, is arranged to cooperate in axial attraction or repulsion, along the pivot axis DA, with at least one such surface 16, 18, 21, 22, to maintain the shaft 10 in an axial service position, in the absence of shock or external disturbance.

 More particularly, at least two polar masses 1 1, 12, 31, 32 cooperate, in geometrical opposition, with at least two surfaces 16, 18, 21,

22, corresponding, to exert on the shaft 10 opposite axial forces and equal. It will be understood that, in the normal operating position, not all the surfaces of the shaft 10 necessarily have to cooperate with all the polar masses of the main structure 100: indeed, the relative cooperation between certain surfaces and certain polar masses exists only in certain relative axial positions of the shaft 10 relative to the main structure 100.

Of course, the surfaces of the shaft may be polar masses arranged to create such a magnetic field, or respectively such an electrostatic field, just as some polar masses of the structure may comprise surfaces made of a magnetic material or conductor, or respectively in an electrified material or electrostatic conductor: both the shaft 10 and the main structure 100 may comprise field generating zones, or / and passive zones reacting to a magnetic field and / or electrostatic.

 According to the invention, in the magnetic application, the axial component, along the axis of pivoting DA, of the resulting magnetic field, ensuring the attraction or the anti-shock axial repulsion, preferably has an intensity greater than 0.55. Tesla, for the case of a steel shaft with a mass of 60 mg.

 Electrostatic application requires fields that limit its application to trees of very small mass, well below 60 mg, and especially less than 10 mg.

 In a particular embodiment that minimizes friction, at least one magnetic field, or electrostatic respectively, tends to attract or repel the shaft 10 radially away from the walls of the housing 14, 15, and to align the shaft 10 on the axis of the housing. pivoting DA. More particularly, at least one of these polar masses 1 1, 12, 31, 32 is arranged to create such a field, close to at least one such surface 16, 18, 21, 22.

 In another variant, at least one magnetic or electrostatic field tends to attract the shaft radially towards a wall of a housing 14, 15. More particularly, at least one of these polar masses 1 1, 12, 31 , 32, is arranged to create such a field, close to at least one such surface 16, 18, 21, 22.

 In an advantageous implementation, the shaft 10 is braked axially along the pivot axis DA only by a magnetic potential, respectively electrostatic, varying along the pivot axis DA and creating a resistive effort resulting from the cooperation in attraction or repulsion between at least one polar mass 1 1, 12, 31, 32, and at least one surface 16, 18, 21, 22.

 More particularly, the profile of this potential is such that this resistive effort is continuously increasing or decreasing during the stroke of the shaft 10 along the pivot axis DA.

More particularly, so as to ensure the transformation of the kinetic energy imparted to the shaft 10 during an acceleration or shock, the shaft 10 is braked axially along the pivot axis DA only by this profile. a potential which forms at least one magnetic field barrier, respectively electrostatic, resulting from the cooperation in attraction or repulsion between at least one polar mass 1 1, 12, 31, 32, and at least one said surface 16, 18, 21, 22 This barrier forms a virtual annular notch, arranged to brake or stop the stroke of the shaft 10 along the pivot axis DA. The passage of such a barrier absorbs part of the kinetic energy of the shaft 10 during an impact. Depending on the configuration of the potential profile, this energy is restored if the barrier forms a potential peak between an increasing ramp and a decreasing ramp potential, or accumulated if the potential profile is stepped, or even sawtooth, with bearings each limited by such a potential barrier.

 More particularly, the shaft 10 is braked axially along the pivot axis DA only by a plurality of such barriers, the passage of each of which absorbs a portion of the kinetic energy of a shock, each barrier thus constituting the limit of a level of potential.

 More particularly, these barriers are successive and have, along the pivot axis DA, magnetic field intensities, respectively electrostatic, which are increasing, from a service position of the shaft 10, towards a mechanical stop that includes the main structure 100, forming a limit switch of the relevant end of the shaft 10.

 In a variant, this mechanical stop is paired with a magnetic stop, or itself constitutes a magnetic stop.

 In a particular embodiment, the shaft 10 is cylindrical

 In a particular embodiment, at least one housing 14, 15, of the main structure 100 is cylindrical. More particularly, the main structure 100 comprises a single bore for housing the shaft 10.

 In a variant for a lateral introduction of the shaft 10, the main structure 100 comprises a lateral cutout 19 extending parallel to the pivot axis DA, and sized to allow lateral insertion and extraction of the shaft 10.

In a variant for axial insertion of the shaft 10, the main structure 100 comprises an end cutout 190 sized to allow insertion and extraction of the shaft 10 along the pivot axis DA. In a particular variant, the main structure 100 comprises a first structure 1 1 comprising at least a first housing 14. The shaft 10 is pivotably movable at least in this first housing 14. This first structure 1 1 creates in this first housing 14, such a magnetic field, or respectively such an electrostatic field, substantially of revolution about the pivot axis DA, to subject the shaft 10 to a force tending to align the shaft 10 along the pivot axis DA. And the main structure 100 comprises, in a second housing 15 arranged at the level of the first structure 1 1 or a second structure 12 that comprises the main structure 100, a limiting surface 120 magnetized, or respectively electrified, arranged to attract or axially pushing along the axis of pivoting DA a magnetized or electrified front surface 18 which the shaft 10 comprises. In the magnetic variant, the intensity of the magnetic field between the front surface 18 and the limiting surface 120 is greater than 0.55 Tesla, for a steel shaft with a mass of 60 mg.

 More particularly, this at least one front surface 18 is of revolution about a shaft axis AA of the shaft 10 which is aligned with the pivot axis DA, when the shaft 10 is in the first housing 14.

 More particularly, the shaft 10 has two such end faces 18 opposite one another, and the watch sub-assembly 200 comprises two said limiting surfaces 120, each arranged to attract or repel such a front surface 18.

 More particularly, the shaft 10 comprises at least one such front surface 18 at a distal end along a shaft axis AA of the shaft 10 which is aligned with the pivot axis DA when the shaft 10 is in the first housing 14.

 More particularly, the shaft 10 has such a front surface 18 at each of its distal ends along this shaft axis AA.

In a particular variant, the shaft 10 comprises at least a first upper surface 16, housed in the first housing 14, and having at least superficially a magnetized or ferromagnetic material, or respectively at least superficially comprising an electrostatic conductive material. This at least one first upper surface 16 is subjected, in this first housing 14, to the magnetic field, or respectively the electrostatic field, generated by the first structure 1 1. And the shaft 10 comprises at least a second lower surface 17 housed in a second housing 15 that includes the structure 1 1 or that comprises a third structure 13 of the watch sub-assembly 200, the second housing 15 constituting a stop, in particular radial.

 More particularly, the second housing 15 surrounds a second structure 12 comprising such a limiting surface 120.

 More particularly, the shaft 10 is of revolution about a shaft axis AA of the shaft 10 which is aligned with the pivot axis DA when the shaft 10 is in the first housing 14. And the shaft 10 comprises at least a first cylindrical upper surface 16 which cooperates with a revolution bore constituting the first housing 14.

 The invention also relates to a movement 500 comprising at least one such watch sub-assembly 200.

 The invention also relates to a watch 1000 comprising at least one such watch sub-assembly 200.

 In a particular embodiment, the structure is ceramic, and comprises, at least in the vicinity of the surface of at least one housing 3, an encrustation of magnets and / or electrets, and / or magnetizable ferromagnetic particles.

 In particular, the housing 3 is smooth.

 In a particular way, the structure 1 comprises or constitutes a ferromagnetic shielding.

 If one compares the invention with the embodiments of the prior art incorporating magnetic elements at the level of guides, the caliber ETA 2894 discloses the use of a magnet for braking a small second wheel in the form of a friction to suppress the floating; in this case the magnetic interaction is used only to dissipate the energy of the mobile, without ensuring the centering of the rotational mobile. The configuration of the shockproof according to the invention differs in that:

- The relative position of the magnet and the ferromagnetic part of the rotational mobile is invariant under rotation, thus avoiding the torque variations due to this asymmetry; the purely mechanical contacts have a minimal contact surface and give an efficient tribology, thus minimizing the dissipation of energy, and therefore of the torque tap;

 - In some variants, a mechanical stop occurs only during shocks, while the magnetic field ensures the recentering of the mobile after shock independently of the shock amplitude: the mechanical and magnetic forces therefore intervene separately.

 Another ETA caliber uses magnets to angularly position a spindle system. In this case, the magnetic configuration imposes a finite holding torque (threshold effect) which opposes the angular displacements. The present invention aims at an exactly opposite function: the magnetic configuration is defined to impose a radial / axial retaining / centering force without a holding torque or angular brake being introduced. In this way, the mobile is free to turn but its centering is assured. Referring to Figure 12, a fundamental feature of the invention is, in the case of axial retention, the cylindrical symmetry of the magnetic system.

 The presence of magnetic attraction is one of the aspects characterizing the invention, in comparison with systems incorporating magnets in repulsion.

 For example, in a system using magnetized parts operating solely in repulsion to generate magnetic levitation, the fine position of the component is therefore not precisely known in time, and it is possible, and even inevitable, that the latter oscillates. around a position of equilibrium, generating friction where there is mechanical contact, and generating operational problems if the amplitude of the oscillation is too great. While in the context of the invention, the magnetic force is, in most applications, used to press with a certain prestressing force the shaft against a mechanical stop. In normal operation the component is therefore in a constant position mechanically fixed.

 The known mechanisms do not exploit the magnetic properties of a component whose magnetic parts are only appendices, because precisely the work in attraction is always avoided.

The use of the magnetic properties according to the invention in an anti-shock function departs from known magnetic applications, focused on levitation or the positioning centering, and where the positioning is very sensitive to tolerances (magnet geometries and remnant fields).

 Indeed, the dissipation of the impact energy is not optimal with a magnetic system, which is highly conservative, and forces to use mechanical stops. In the invention, the recentering (radial for example in the case of Figure 9) is a side effect of the anti-shock system (axial).

 FIGS. 10 and 11 show variants in which the different magnetic fields in the presence are not coaxial, and the interactions between components can be particularly oblique.

 The operation of a system according to the invention, with magnets now in mechanical contact, however makes it possible to be insensitive (for positioning) to the tolerances of the magnet.

 The main advantage of the magnetic anti-shock for a tree is the dependence of the restoring force as a function of the displacement of the shaft, in the axial direction for example. Just as for a traditional anti-shock, a prestressing force, or a holding force in the case of the magnetic shock absorber, forces the component not to move during small impacts. Beyond this shock amplitude, the restoring force of a traditional anti-shock increases with the distance of the component, because of the loading of the spring, while that of a magnetic shock absorber according to the invention decreases. with the distance of the component. This characteristic makes it possible to really decouple two different regimes: one where the shocks have small amplitudes, and the second one with larger shock amplitudes, with a plateau value of shocks from which the energy is stored mechanically or dissipated. , by a stop for example.

 In practice, a prestressing force is often observed which varies greatly with the tolerances. To delegate this force of pre-stress to the magnetic force makes it possible to depend on the mechanical spring only by its rigidity during the damping beyond a given amplitude of shock (big shocks).

 The invention is distinguished by different advantages:

- To avoid torque variations due to possible asymmetry, we can build the relative position of the magnet and the ferromagnetic part of the invariant shaft under rotation; - purely mechanical contacts can be minimized, thanks to magnetic or electrostatic axial retention, particularly in the repulsion configuration without stop, and, in the case where these mechanical contacts are maintained, they have a minimum contact surface and giving tribology efficient, with minimization of the energy dissipation, and thus of the torque;

 these contacts may be as identical or larger than with a traditional friction spring, and thus make it possible to exploit the dissipation of energy to damp the floating of a needle or the like;

 - In some embodiments of the invention, a mechanical stop occurs only during significant impacts, while the magnetic field provides the recentering of the shaft after the shock, regardless of the amplitude of the shock, and the maintenance of the shaft in position during weak impacts: the mechanical and magnetic forces therefore intervene separately;

 the magnetic or electrostatic configuration is defined in order to impose a radial / and / or axial retaining / refocusing force, without a holding torque or an angular brake being introduced into the system. In this way, the shaft is free to turn, and its centering is assured. An advantageous characteristic of certain variants of the invention is the cylindrical symmetry of the magnetic system around the pivot axis DA;

the dependence on respect of tolerances is less important than in the prior art;

 the problems related to the wear due to the shocks on the watch are greatly reduced, since they only concern the rare cases where the shaft comes into contact with a mechanical stop in the case of the most important shocks;

- the cooperation of the fields ensures a fine refocusing after a shock;

 - the highly elastic response of magnetic fields allows better control of friction;

 the variants presented make it possible to decouple the axial and radial stress, which are treated separately;

- It is now possible to fix any tree in a movement, by magnetic or electrostatic forces;

- it is possible to treat the shocks of different amplitudes differently, by making work components (or parts of components) different for dissipation. One can imagine an amplitude below which the magnetic force is exploited, and above which the dissipation is mechanical.

 The horological achievements in the magnetic variant function correctly with an axial field of 0.55 Tesla.

 A particular embodiment relates to a steel shaft with a mass of 60 mg, held in contact by a magnet, in attraction, and with an axial field of 0.55 Tesla, the shaft has a diameter (for the near part magnet) of 0.15 mm, with NeFeB magnets having a remanence of 1.47 T, and is plated with a holding force sufficient to withstand shocks with accelerations below 75 g if the magnet has a height of 0.8 mm and a radius of 0.45 mm; the calculation takes into account the presence of a tribological layer with a thickness of 60 μηι between the shaft and the magnet. A typical magnetic potential variation between the mechanical stop and the contact in the operating position is 6 μύ for 0.1 mm of displacement, particularly in the case of this example. With a variation twice as large (0.12 J / m), it is possible for example to achieve two potential levels, which occur during two different shock conditions (0-100 g and 100-200 g).

With regard to the electrostatic variant, for similar applications, it is appropriate to provide between 0.5 and 50 mC / m ^A 2 (a field of approximately 0.01 - 1 MV / m).

 It is therefore possible to use a system according to the invention to replace a mechanical friction spring. The possible mechanical friction generated by this system is not necessarily a disadvantage, and can be exploited, including in the case of a radial maintenance where the friction against the chimney is important. The friction can be exploited to dissipate the energy of the floating of a mobile such as a needle.

 We can still combine this mechanical friction due to the maintenance in contact, and a braking type of eddy currents.

 In sum, the invention allows the decoupling of functions during shocks, depending on their amplitude:

- For a system holding the axis in abutment, for example by means of unbalanced magnets, the magnetic force keeps the axis in contact during low shocks but decreases sharply when the impact is large enough to make it take off. It is then a mechanical stop that takes over; for a system with a magnetization varying along the axial direction, several displacement values in this direction are defined as a function of the intensity of the impact, up to a maximum where the axis dissipates the remaining energy in abutment.

Claims

R EVE NDI CAT IO NS

 1. Watch sub-assembly (200) for a watch, comprising a main structure (100) and a shaft (10) movable pivotally about a pivot axis (DA) in at least one housing (14; 15) of said main structure (100), said shaft (10) having at least one surface (16; 18; 21; 22) in a magnetized material or magnetic conductor, or respectively in an electrified or electrostatically conductive material, and said main structure (100) having at least one at least one polar mass (1 1; 12; 31; 32) arranged to create, near at least one said surface (16; 18; 21; 22), at least one magnetic field, or respectively an electrostatic field, for an axial and radial retention of said shaft (10), characterized in that at least one said polar mass (1 1; 12; 31; 32) is arranged to cooperate in axial attraction and repulsion and radial, according to said pivot axis (DA ), with at least one said surface (16; 18; 21; 22) for absorbing a c hoc and return said shaft (10) to the service position after cessation of said shock, and characterized in that at least one polar mass (1 1; 12; 31; 32) is arranged to create, in proximity to at least one said surface (16; 18; 21; 22), at least one said magnetic or electrostatic field, which either tends to radially attract said shaft (10) to a wall of said housing (14; 15), or varies along the pivot axis (DA) and is arranged to apply to said shaft (10) a resistive force resulting from cooperation in attraction or repulsion between at least one said polar mass (1 1; 12; 31; 32) and at least one said surface (16; 18; 21; 22).

2. watch sub-assembly (200) according to claim 1, characterized in that at least one said field provides said attraction or repulsion of said shaft (10) axially, and is substantially of revolution about said pivot axis (DA) , is a magnetic field, and in that its axial component, along said pivot axis (DA), has an intensity greater than 0.55 Tesla.

3. Watchmaking subassembly (200) according to claim 1 or 2, characterized in that said shaft (10) is braked axially along said pivot axis (DA) only by a magnetic potential, respectively electrostatic, varying along the length pivot axis (DA) and creating a resistive force resulting from the cooperation in attraction or repulsion between at least one said polar mass (1 1; 12; 31; 32) and at least one said surface (16; 18; 21; 22).

4. Watchmaking subassembly (200) according to claim 3, characterized in that the profile of said potential is such that said resistive force is continuously increasing or decreasing during the stroke of said shaft (10) along the pivot axis (DA ).

5. Watchmaking subassembly (200) according to claim 3 or 4, characterized in that said shaft (10) is braked axially along said pivot axis (DA) by said potential profile which forms at least one magnetic field barrier. , respectively electrostatic, said barrier forming a virtual annular notch, arranged to brake or stop the stroke of said shaft along said pivot axis (DA).

6. Watchmaking subassembly (200) according to claim 5, characterized in that said shaft (10) is braked axially along said pivot axis (DA) only by a plurality of said barriers whose passage of each absorbs a portion of the kinetic energy of a shock, each said barrier constituting the limit of a potential plateau.

7. Watchmaking subassembly (200) according to claim 5 or 6, characterized in that said barriers are successive and have, according to said pivot axis (DA), magnetic field intensities, respectively electrostatic, which are increasing, since a service position of said shaft (10) towards a mechanical stop that comprises said main structure (100).

8. Watchmaking subassembly (200) according to claim 7, characterized in that said mechanical stop is paired with a magnetic stop or constitutes a magnetic stop.

9. Watchmaking subassembly (200) according to one of claims 1 to 8, characterized in that said main structure (100) comprises a first structure (1 1) comprising at least a first housing (14), at least in wherein said shaft (10) is pivotally movable, said first structure (1 1) creating in said first housing (14) a said magnetic field, or respectively said electrostatic field, substantially of revolution about said pivot axis (DA), for subjecting said shaft (10) to a force tending to align said shaft (10) along said pivot axis (DA), and in that said main structure (100) comprises, in a second housing (15) arranged at the level of said first structure (1 1) or a second structure (12) that comprises said main structure (100), a magnetized or respectively electrised limiting surface (120) arranged to attract or repel axially along said pivot axis (DA) a front surface (18) magnetized or respectively electrified that includes said shaft (10).

 Watchmaking subassembly (200) according to claim 9, characterized in that said field is a magnetic field and that its intensity between said front surface (18) and said limiting surface (120) is greater than 0.55 Tesla .

 1 1. Watchmaking subassembly (200) according to claim 9 or 10, characterized in that said shaft (10) comprises at least a first upper surface (16) housed in said first housing (14) and having at least superficially a magnetic material or magnetic conductor, or respectively at least superficially comprising an electrostatic conductive material, said at least one first upper surface (16) being subjected, in said first housing (14), to said magnetic field, or respectively electrostatic field, generated by said first structure ( 1 1), and characterized in that said shaft (10) comprises at least a second lower bearing surface (17) housed in a second housing (15) that comprises said structure (1 1) or that comprises a third structure (13) of said watch sub-assembly (200) said second housing (15) constituting an abutment

 12. watch sub-assembly (200) according to claim 1 1, characterized in that said second housing (15) surrounds a said second structure (12) having a said limiting surface (120).

 13. Watchmaking subassembly (200) according to one of claims 9 to 12, characterized in that said shaft (10) is of revolution about a shaft axis (AA) of said shaft (10) which is aligned with said pivot axis (DA) when said shaft (10) is in said first housing (14), and in that said shaft (10) has at least one first cylindrical upper surface (16) which cooperates with a revolution bore constituting said first housing (14).

 14. Movement (500) comprising at least one watch sub-assembly (200) according to one of claims 1 to 13.

 15. Watch (1000) comprising at least one watch sub-assembly (200) according to one of claims 1 to 13.