CH710978A2 - Watch sub-assembly comprising a magnetic shock absorber for a watch shaft. - Google Patents

Abstract

The invention relates to a horological sub-assembly (200) for a watch, comprising, pivoting in a housing (14; 15), a shaft (10) comprising at least one surface (16; 18) magnetized or magnetic conductor, respectively electrified or electrostatic conductor, and comprising at least one polar mass (11, 12) subjecting a said surface (16; 18) to a magnetic field, or electrostatic respectively, of revolution about an axis (DA). At least one said polar mass (11, 12) cooperates in attraction or axial repulsion with said surface (16; 18), to absorb an impact and return said shaft (10) to the service position after cessation of said shock.

Description

Field of the invention

The invention relates to a watch sub-assembly for a watch, comprising a main structure and a movable shaft in pivoting about a pivot axis in at least one housing of said main structure, said shaft comprising at least one surface in a magnetic or ferromagnetic material, or respectively in an electrified or electrostatic conductive material, 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 axial or / and radial retention of said shaft.

[0002] The invention also relates to a movement comprising at least one such sub-assembly.

[0003] The invention also relates to a watch comprising at least one such sub-assembly.

[0004] The invention relates to the field of watch movements comprising pivoting mechanical components.

Background of the invention

[0005] In watchmaking, and more particularly for watches, mechanical technology is generally used to hold a component, in particular a shaft, in a particular position. It can be a stopper hold thanks to an elastic system, especially when a certain freedom of movement is necessary in the event of an impact. For example, a spring keeps a shaft in abutment.

[0006] The maintenance by a pre-stressed spring is not stable over time: such a spring, which must work with stress variations due to the shocks undergone by the watch, is subject to fatigue and to wear, as well as each component which is subjected to abutment percussion forces.

[0007] In addition, the manufacture of such a spring is difficult to reproduce. The clearance of tolerances can, again, cause a large dispersion in the value of the pre-stressing force. As a result, the performance is not stable over time, and the shockproof effect also deteriorates over the life of the watch.

[0008] In short, the main problems encountered with mechanical elastic retention systems are the wear of the components caused by repeated mechanical stresses, and the need to produce with tight tolerances, and therefore costly.

[0009] It therefore remains difficult to ensure the axial retention of a watch shaft, with an unalterable shock-proof mechanism.

Summary of the invention

[0010] The invention proposes to define an architecture for maintaining a watch shaft in position, which is capable of ensuring a stable shockproof effect over time, and which is reproducible.

[0011] To this end, the invention relates to a watch sub-assembly for a watch according to claim 1.

[0012] The invention also relates to a movement comprising at least one such sub-assembly.

[0013] The invention also relates to a watch comprising at least one such sub-assembly.

Brief description of the drawings

[0014] Other characteristics and advantages of the invention will become apparent on reading the detailed description which follows, with reference to the accompanying drawings, where: FIG. 1 represents, schematically and in perspective, 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 corresponding substantially to the axis of the first bore; this shaft is maintained axially by a second front pole mass, in a chamber defined here by a second bore which comprises a substantially tubular limiting sleeve; this sub-assembly is shown without its possible positioning stops; fig. 2 represents, schematically and in section, the sub-assembly of FIG. 1; fig. 3 represents, schematically and in top view, the sub-assembly of FIG. 1; figs. 4 and 5 show, respectively in section and in top view, another similar subassembly, where the first pole mass is of revolution around the shaft; fig. 6 shows, schematically and in section, a covering or movement sub-assembly according to the invention, in a first variant which comprises a radial mechanical guide, and at least one magnet which ensures the axial holding of a shaft in an axial direction; this sub-assembly 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 has an upper wing, limiting the travel of the insert and forming a safety stop above the shaft; fig. 7 shows, similarly to FIG. 1, a reverse configuration, where the safety stopper is below the shaft, and where a tribological surface is introduced on the stopper; fig. 8 shows, schematically and in section, a magnet and a magnetic part in attraction, constituting a structure and a shaft each comprising, at their respective contact surfaces, a tribological or anti-wear layer; fig. 9 represents, schematically and in section, a structure with a magnetic housing receiving a magnet in the form of a headed nail, which comes to press a spacer forming part of a shaft and which is held captive and pressed against the structure by this magnet , pinched between the head of the magnet and the fixed element; fig. 10 represents, in a diagrammatic way, partial and in section along its axis, a shaft comprising several magnets, the polarity of which is shown schematically by hatching or by a cross, and which is movable between other fixed magnets that comprises a structure in which this tree is mobile; fig. 11 shows another configuration of a shaft carrying magnets between other fixed magnets of the structure; fig. 12 shows, schematically, partial and in section, a structure in the form of a fixed line in a direction z, comprising an alternation of parts, on the one hand paramagnetic or ferromagnetic, and on the other hand diamagnetic, respectively schematized by hatching and by a cross, along which structure, which is fixed, can be aligned a cylindrical shaft comprising a permanent magnet, not shown; fig. 13 shows, schematically and in front view, a watch comprising a movement which comprises such a sub-assembly; fig. 14 shows, schematically, partially and in section passing through the pivot axis of its shaft, a timepiece subassembly according to the invention, comprising a pivotally movable shaft in a structure, where the shaft generates a 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 where the structure in which the shaft is movable comprises a succession of zones generating fields of the conical type, tending to oppose the fields generated by the tree, and which have, from a service position of the tree illustrated in FIG. 14A, increasing intensities as the lower part of the shaft stroke approaches; each of these field areas of the structure constitutes a virtual notch, which slows down the tree in its downward course: fig. 14B shows the sub-assembly of FIG. 14A after a shock or a strong acceleration, the shaft starting a stroke towards a lower limit switch not shown, and in a position where this shaft has just crossed a first field barrier symbolized by simple arrows, substantially symmetrical and opposite to the conical field which the tree itself comprises, and where the tree arrives on a second field barrier, of axial intensity greater than that of the first barrier, and symbolized by double arrows, FIG. 14C shows the same sub-assembly in the case where the kinetic energy imparted to the tree is high and allows it to cross this second field barrier, and where the tree arrives on a third field barrier, of axial intensity greater than that of the second barrier, and symbolized by triple arrows, and which, in this example, is sufficient to stop the axial travel of this shaft, FIG. 14D shows the subsequent raising of the shaft to its service 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 where the shaft generates only one end axial field, and where the third conical barrier at the lower end of the stroke is replaced by an axial field barrier of similar intensity, and a sequence of lowering and raising the shaft on its axis which is similar to that of FIG. 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, similarly to FIG. 16, a variant where the fields generate forces of attraction instead of forces of repulsion; fig. 16B illustrates, similarly to FIG. 16, a variant where the radial fields generate forces of attraction instead of forces of repulsion, while the axial fields of the structure generate forces of repulsion; fig. 17 illustrates, in perspective in view 17A and in top view in view 17B, a sub-assembly according to FIG. 16, comprising a lateral cutout parallel to the pivot axis of the shaft and allowing its insertion and extraction; fig. 18A is a schematic perspective view of a mechanism using the system of FIG. 12, with a shaft having in the middle part a dark permanent magnet placed near the line-shaped structure, here in the form of a concave shell with alternating diamagnetic and paramagnetic / ferromagnetic zones; fig. 18B is a section through the assembly of FIG. 18A, and fig. 18C illustrates the polarities generated by the presence of the permanent magnet, attached to the shaft, and by the magnetic properties of the areas on the hull; the shaft fitted with a permanent magnet then experiences a force similar to the versions in fig. 10 to 12, but generated by diamagnetic and paramagnetic / ferromagnetic zones; figs. 19A and 19B are similar to Figs. 18B and 18C, but for a system using maintenance in mechanical contact, the part shown in crosses being fixed; fig. 20 is a curve with the magnetic force exerted on the ordinate 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 on the ordinate 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 view, partially and in section, of a timepiece movement comprising a sub-assembly according to the invention, with a shaft axially attracted by a pole mass, and the end of which is in friction on the front part of the this one.

Detailed description of the preferred embodiments

[0015] The effects of mechanical stresses in a component depend on a large number of parameters, the tolerance range of which is often wide. The consequences of friction and wear are particularly difficult to control, as they strongly depend on the surface conditions and the physical properties of the materials used.

[0016] These properties themselves depend on the alloys used and the processes used, in particular heat and surface treatments and ion implantation. The accumulation of the tolerances specific to the various process and material parameters makes it impossible to know and control precisely these physical properties. And reproducibility is therefore not guaranteed, due to these tolerances. Or the reduction of the tolerance ranges, which makes it possible to obtain better reproducibility of the phenomena, leads to costs that are 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 understood, and the difficulty in solving these equations analytically and numerically with the smallest approximations possible. However, from a macroscopic point of view these inaccuracies are low enough to make magnetic systems inherently reliable.

[0018] The invention proposes an anti-shock type watch shaft maintenance in an unalterable manner, under the effect of a magnetic and / or electrostatic field.

[0019] It is more particularly described with non-limiting examples of a magnetic application. The invention can also be implemented with the use of electrostatic fields, in particular through the use of electrets. Or even by combining magnetic fields and electrostatic fields.

[0020] The term "shaft" is understood here to mean any timepiece component arranged to pivot about a theoretical pivot axis. The invention is described below mainly for the shaved parts of such a component, or mobile, or the like. For example, in the case of a balance, we will be more particularly interested in the ends of the shaft part of this balance. The invention is illustrated in a simplified manner with a shaft of revolution, comprising one or more cylindrical seats. But this illustration is in no way limiting, the invention can be applied to any type of component, such as anchor, escapement wheel, wheel, pinion, or the like.

[0021] It is proposed, in these examples, to use the magnetic forces in order to construct an axis retention 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:

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

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

A first variant, in FIG. 1 to 3, consists of using magnetic force to force a shaft in all three directions, for example by keeping it in contact in a triangle which positions it (positioning stops). Contact can also be made directly on the permanent magnets.

[0024] A second variant, in FIG. 4, with radial mechanical guidance and a magnet which provides axial holding, relates to cases where magnetic force is used to force a shaft in one or two of the three directions, while mechanical guidance is used to limit its displacement in the other directions. Typically, the radial guidance can be performed via a chimney while the shaft is held axially by a magnet.

[0025] 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 axial holding in z in fig. 1 to 4. This has the advantage of averaging component defects, and exerting stress, especially force, over a larger 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 couples, induced on a piece of magnetized material or of ferromagnetic material immersed in a magnetic field. This effort depends on the magnetization of the material, or its magnetic permeability, and the strength 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 tree undergoes (or generates, in the case where it is itself magnetized and cooperates with a magnetized or non-magnetic ferromagnetic environment) an attraction or repulsion force which can be used to hold it in place.

[0027] For light elements, and if the bulk allows the presence of one or more magnets capable of generating a sufficient magnetic field, the magnetic force alone may be sufficient to retain an element during impacts.

[0028] However, in most cases this force is too low. When the magnetic force is too weak to withstand a shock, it is possible to introduce a safety stopper limiting too great a displacement, as shown in fig. 6 and 7, which show two configurations of the type of FIG. 4, with a safety stop, once above the component and once below, and potential contact zones referenced 5. The magnetic hold is therefore used to counter low shocks, with a limiting amplitude from which the component comes off to go into abutment. This operating mode has the advantages of spring holdings, while causing a lower shock when returning to position. This is because the magnetic system, as opposed to the spring, exerts a force that decreases with the distance of the part from its held position. The energy stored during an accidental impact (which is released when the component returns to position) is therefore lower.

[0029] The force can also be generated by two magnets. Figs. 20 and 21 show the magnetic force Fm, in Newtons, which 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 h1 / h2 ratio of the relative size of these two bodies.

In a further variant, the magnetic system not only has a holding role, but also makes it possible to facilitate the function of putting on / putting it back in place, as shown in FIGS. 10 and 11. In the first case of FIG. 10, an additional force must be applied to overcome the repulsion of the magnets, and, once the system is in place, it is held there in the axial z direction; 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-like structure made up of attractive and repulsive parts. These parts can also be made of permanent magnets. The radial resistance of this system is magnetic via the attractive parts (with the possibilities of variants presented above); the component is magnetically recentered after each impact. This system is easily adaptable for an angular degree of freedom.

[0031] The line-shaped structure of FIG. 12, with attractive and repellent regions can also be directly on the shaft, with a permanent magnet on the stationary part of the movement.

[0032] Different geometric configurations can thus be used.

We can thus use the magnetic force to force 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 stops. positioning. The magnetic elements may be set back from the contact surfaces. Contact can also be made directly on the surfaces of magnetic components.

[0034] A variant relates to cases where the magnetic force is used to force an element in one or two of the three directions, while mechanical guidance is used to limit its displacement in the other directions.

[0035] Thus, the invention is more precisely described with regard to the axial damping of a shaft. The pivoting of the shaft can be traditional, by guiding in a stone or a bearing, or even be of the magnetic type, or other, in particular combined.

For each of these variants, when the magnetic force is too low to withstand a shock, it is possible to introduce a safety stop, so as to limit the movement of the shaft and avoid too great a stroke . Magnetic hold is therefore used to counter weak shocks, with an amplitude from which the magnetically held shaft peels off to go to a mechanical safety stop. This operating mode has the advantages of spring holdings, while causing a lower shock when returning to position. This is because the magnetic system, as opposed to the spring system, exerts a force which decreases with the distance of the shaft from its service position, held. The energy stored during an accidental impact, and 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 / and electrostatic fields present at the level of the structure or / and of the shaft is sequenced, and comprises electromagnetic barriers which depend on the relative position of the tree and the structure, and the passage of each of which consumes all or part of the kinetic energy of the tree during an impact.

[0038] The relative force can be generated by two magnets, or by a magnet near a ferromagnetic (attraction), diamagnetic (repulsion) or paramagnetic (attraction) part.

[0039] The shaft to be kept in place may itself be ferromagnetic, diamagnetic or paramagnetic and be located near a magnet, or else itself include one or more magnets or magnetized areas, or respectively electrified.

[0040] In the case where the force is caused by two magnets, the latter can work in attraction or repulsion; the work in attraction theoretically generates a slower aging of the magnetic system. The repulsion mode is however easier to implement for a damping at the end of the shaft, and this non-limiting mode is described in the examples illustrated.

[0041] The damping characteristics according to the invention, by magnetic or electrostatic means, are good for low or medium shocks. If it is possible to use this technology for the complete absorption of the exceptional kinetic energy of the shaft during an impact, it is clear that this is at the expense of bulk. Also the invention is preferably combined with a conventional mechanical stop, which can be a straight stop, or a bearing surface of a spring which is not in contact with the shaft during low or medium impact. . Preferably, any magnet surface is protected, because of its fragility, by another surface that includes, as the case may be, 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 part 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 absorber of the shaft, are also used to ensure axial retention of the shaft in its service position. . It will be understood that contacts are completely avoided only in repulsion configurations as in FIG. 16. In most other cases, even when working in repulsion, shaft contact is inevitable. The circumferential friction dissipates more energy than the friction on the front part.

[0043] The invention lends itself particularly well to 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.

[0044] In this regard, it is noted that a magnetic or electrostatic cooperation between the shaft and the receiving structure is not necessarily only axial.

[0045] Advantageously, this cooperation provides radial support, in order to permanently tend to align the shaft 10 on its theoretical pivot axis DA. Therefore, even if the traditional pivoting guidance of shaft 10 is not perfect, this guidance is optimized by the influence of magnetic or electrostatic fields which tend to realign shaft 10 permanently along its axis DA.

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

In an alternative of traditional guiding of the shaft in the structure, by means of contact surfaces, these surfaces can undergo an adaptation to optimize their tribological, or / and mechanical, or / and anti- properties. wear. A surface layer, such as visible in fig. 8, also achievable on the variant of FIG. 9, or others, may, for example, be corundum, diamond or a protective coating. This surface layer can also be made from a material combining particular tribological and magnetic properties, such as tungsten carbide, in particular with a cobalt binder.

[0048] For light elements, and if the bulk allows the presence of one or more magnets capable of generating a sufficient magnetic field, the magnetic force alone may be sufficient to retain an element during impacts.

Different geometric configurations can be used. In the examples illustrated, the magnetic forces (forces or / and torques) are used in order to build a shaft holding system, exploiting the forces induced on a piece of magnetized material immersed in a magnetic field. To do this, we position one or more magnets preferably on a fixed part, and we exploit the magnetic force undergone by a ferromagnetic (attraction), diamagnetic (repulsion) or paramagnetic (attraction) component that must be fixed. This component will therefore undergo an attraction or repulsion force which can be used to hold it in place. Inverse relative positioning is also possible.

A variant shown in FIGS. 1 to 3 consists in using a magnetic force to force a shaft 10 in all three directions, for example by maintaining it in a trihedron which positions it, or else 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 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 11 and this second structure 12 are magnets. A third structure 13 has a bore 15 which limits the radial movement of a bearing surface 17 of the shaft 10.

Another variant, shown in FIGS. 4 and 5, illustrates the cases where the magnetic force is used to force a shaft 10 in one or two of the three directions, here in the axial direction corresponding to the pivot axis DA, while a mechanical guide is used for limit the movement of the shaft 10 in the other directions. Typically, the radial guidance can be performed via a chimney, at a bore 14 of a first structure 11, while the shaft 10 is held axially by a magnet that a second structure 12 has.

[0052] 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 simple magnet for axial holding in the axial direction, in the examples of fig. 1 to 5, thus has the advantage of averaging component defects, and of exerting stress on a larger radius. This can be an advantage if the mechanism is arranged to exploit eddy current dissipation, to increase the friction capacities of a magnetic equivalent of a friction spring.

The preferred solution, but not limiting, thus uses a magnetic force of attraction, either between two magnets, or between a magnet and a magnetically conductive part, in particular ferromagnetic. It allows better stability and better control over the 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 part is ferromagnetic, and will therefore magnetize in accordance with the magnet: in this case, the force is attractive. Only in the case where the magnetic part 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 pulling force, the direction of the forces tends. when the parts are brought together, the force is negative, either in the ferromagnetic magnet-part variant, or in the variant with two magnets.

[0056] Only FIG. 5 corresponds to a solution where the forces of attraction and repulsion are combined to stabilize the position of the component.

[0057] The repellent solutions, in turn, dissipate some or all of the energy of the shocks by magnetic repulsion rather than by mechanical shock.

[0058] For light trees, and if the size allows the introduction of a sufficient number of magnets, the magnetic force alone may be sufficient to retain a tree during impacts. However, in most cases this effort, limited by size constraints, is too low. When the magnetic force is too weak to withstand a shock, it is possible, as shown in fig. 6 or 7, to introduce a safety stop limiting excessive movement. These two configurations show a safety stop, once above the component in fig. 6, and once below in fig. 7. Magnetic hold is therefore preferentially used to counter weak shocks, with a limiting amplitude, 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 operating mode has the advantages of spring retention, while causing a lower shock when returning to the normal service position. In fact, the magnetic system, as opposed to the spring, exerts a force which decreases with the distance of the shaft from its held position. The energy stored in an accidental impact, which is released when the component returns to position, is therefore lower.

In FIGS. 1 to 5, the contact is not shown. This contact can be a direct contact of the magnet with the shaft, as in fig. 8, or a part of the shaft to be held against a positioning stop (not necessarily magnetic) as in fig. 9. The surface against which the contact is maintained can be adapted to optimize its tribological and mechanical properties. The red surface can 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 maintaining, and also makes it possible to facilitate the function of putting on / putting it back in place, as shown in FIGS. 10 to 12.

In the first case of FIGS. 10 and 11, when the shaft is axially introduced into a bore in the structure, additional force must be applied to overcome the repulsion of the magnets, but once the system is in place it is held there 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.

[0062] The second case of FIG. 12 is a magnetic recentering system where the shaft 10 has permanent magnets, and is held against a line-like structure composed of attracting parts and repelling parts. These parts can also be made of permanent magnets. The radial resistance of this system is magnetic via the attractive parts, with the possibilities of variants presented above; the tree is magnetically recentered after each shock. This system is easily adaptable for an angular degree of freedom. Such a line-like structure with attractive and repellent regions can also be directly on the shaft 10, with a permanent magnet on the structure, linked to a fixed part of the watch movement.

[0063] Figs. 18A, 18B, 18C, show a mechanism using the system of FIG. 12. Figs. 18A and 18B show a shaft having a permanent magnet placed near 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. Fig. 18C illustrates the polarities generated by the presence of the permanent magnet (attached to the shaft) and by the magnetic properties of the areas on the hull. The shaft fitted with a permanent magnet then experiences a force similar to the versions in fig. 10 to 12, but this force is here generated by diamagnetic and paramagnetic / ferromagnetic zones.

[0064] Figs. 19A and 19C are similar to Figs. 18B and 18C, but for a system using a maintenance in mechanical contact, the part drawn in crosses being fixed.

[0065] 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 of revolution. This is not necessarily embarrassing, since it is only a transitional regime, and therefore we can consider different configurations: the magnets of the shaft are of revolution (and not those of the chimney) so the direction where the anti-shock function is maximum is fixed on the movement; this direction can correspond, for example, to a direction which statistically receives more shocks; the chimney magnets are of revolution (and not those of the shaft) so the direction where the anti-shock function is maximum is fixed on the shaft; this direction can 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 that are not revolving are not located on either side; thus maintaining mechanical contact on one side ensures the radial positioning of the shaft.

These solutions allow more axial positioning (with mechanical guidance for the radial part) 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 a radial recentering thanks to the repulsion, with an axial positioning in abutment by the magnetic force. The variant of axial magnetic attraction at the end, not shown, is particularly interesting.

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

Another variant is to add a front magnet on the fixed structure, so as to help the axial holding 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 shocks d 'greater amplitudes (where a stop takes over).

We can imagine different types of magnetic potential profiles, and in particular a staircase variant, where more and more energy is absorbed as the shaft moves towards its stop. Another variant has real barriers, which technically only temporarily absorb energy, since the energy is returned as soon as the tree leaves the barrier area.

If the variant shown in FIG. 14 relates to a structure, in which the shaft is mobile, which comprises a succession of zones generating fields of conical type, tending to oppose the fields generated by the tree, and which have, from a service position of the 'tree of increasing intensities as the lower part of the stroke of the shaft approaches, it is understood that other variants may concern: a succession of zones generating fields which tend to line up with the fields generated by the tree; or / and fields with decreasing intensities as the lower part of the shaft stroke approaches.

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

[0074] FIG. 22 illustrates the case of a shaft attracted axially by a pole mass, and the end of which is in friction on the front part thereof.

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

[0076] Of course, if in 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 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 introduce a ferromagnetic shielding or to use the middle part as such.

More particularly, the invention relates to a horological subassembly 200 for a watch, comprising a main structure 100 and a shaft 10. This shaft 10 is movable in pivoting 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 a magnetic conductor, or respectively in an electrified material or an electrostatic conductor. A ferromagnetic or diamagnetic or paramagnetic material is called a “magnetic conductor” here.

To cooperate with this shaft 10, the main structure 100 comprising at least one pole mass 11, 12, 31, 32, which is arranged to create, near at least one such surface 16, 18, 21, 22 , at least one magnetic field, or respectively an electrostatic field, for the axial or / and radial maintenance of the shaft 10 with respect to the pivot axis DA

[0081] In the case of axially holding the shaft 10, this field is substantially of revolution about the pivot axis DA.

In one variant, the main structure 100 comprises at least one pole mass 11, 12, 31, 32, arranged to create, near at least one such surface 16, 18, 21, 22, in addition to the field intended for the axial maintenance of the shaft 10, at least one magnetic field, or respectively an electrostatic field, for a radial maintenance of this shaft 10.

According to the invention, at least one such pole mass 11, 12, 31, 32, is arranged to cooperate in axial or / and radial attraction or repulsion, 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.

Preferably, at least one such pole mass 11, 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 keep the shaft 10 in an axial service position, in the absence of shock or external disturbance.

Preferably, at least two pole masses 11, 12, 31, 32, cooperate, in geometric opposition, with at least two surfaces 16, 18, 21, 22, corresponding, to exert axial forces on the shaft 10 opposite and equal. It is understood that, in the normal service position, all the surfaces of the shaft 10 do not necessarily have to cooperate with all of the pole masses of the main structure 100: in fact, the relative cooperation between certain surfaces and certain pole masses exists only in certain relative axial positions of the shaft 10 with respect to the main structure 100.

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

According to the invention, in the magnetic application, the axial component, along the pivot axis DA, of the resulting magnetic field, ensuring the axial anti-shock attraction or 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, for its part, requires fields which limit its application to trees of very small mass, much less than 60 mg, and in particular less than 10 mg.

In a particular embodiment which minimizes friction, at least one magnetic field, or respectively electrostatic, tends to attract or radially push back the shaft 10 away from the walls of the housing 14, 15, and to align this shaft 10 on the 'DA pivot axis.

In another variant, at least one magnetic field, or respectively electrostatic, tends to attract the shaft 10 radially towards a wall of a housing 14, 15.

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 force resulting from cooperation in attraction or repulsion between at least one pole mass 11, 12, 31, 32, and at least one surface 16, 18, 21, 22.

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

More particularly, so as to ensure the transformation of the kinetic energy communicated to the shaft 10 during an acceleration or a shock, the shaft 10 is braked axially along the pivot axis DA only by this potential profile which forms at least one magnetic field barrier, respectively electrostatic, resulting from the cooperation in attraction or repulsion between at least one pole mass 11, 12, 31, 32, and at least one said surface 16, 18, 21 22. This barrier forms a virtual annular notch, arranged to slow down or stop the travel of the shaft 10 along the pivot axis DA. The passage of such a barrier absorbs part of the kinetic energy of shaft 10 during an impact. Depending on the configuration of the potential profile, this energy is restored if the barrier forms a peak of potential between an increasing ramp and a decreasing ramp of potential, or else accumulated if the potential profile is stepped, or even sawtooth, with stages 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 part of the kinetic energy of an impact, each barrier thus constituting the limit of a potential step.

More particularly still, 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 comprises the main structure 100, forming a limit switch of the end concerned of the shaft 10.

In one variant, this mechanical stop is combined 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 has 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 dimensioned to allow the lateral insertion and extraction of shaft 10.

[0100] In a variant for an axial introduction of the shaft 10, the main structure 100 has an end cutout 190 sized to allow the insertion and extraction of the shaft 10 along the pivot axis DA.

[0101] In a particular variant, the main structure 100 comprises a first structure 11 comprising at least a first housing 14. The shaft 10 is movable in pivoting at least in this first housing 14. This first structure 11 creates, in this first housing 14, such a magnetic field, or respectively such an electrostatic field, substantially of revolution around the pivot axis DA, to subject the shaft 10 to a force tending to align this 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 11 or of a second structure 12 that the main structure 100 comprises, a limiting surface 120 magnetized, or respectively electrified, arranged to attract or repel axially along the pivot axis DA a front surface 18 magnetized, or respectively electrified, that comprises the shaft 10. In the magnetic variant, the intensity of the magnetic field, between the front surface 18 and the limiting surface 120 is greater at 0.55 Tesla, for a steel shaft with a mass of 60 mg.

[0102] 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. accommodation 14.

[0103] More particularly, the shaft 10 comprises two such end surfaces 18 opposed to 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.

[0104] 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 accommodation 14.

[0105] More particularly, the shaft 10 has such a front surface 18 at each of its distal ends along this axis AA shaft.

[0106] In a particular variant, the shaft 10 comprises at least a first bearing surface 16, housed in the first housing 14, and comprising at least superficially a magnetic or ferromagnetic material, or respectively comprising at least superficially an electrostatic conductive material. This at least a first bearing surface 16 is subjected, in this first housing 14, to the magnetic field, or respectively electrostatic field, generated by the first structure 11. And the shaft 10 comprises at least one second bearing surface 17 housed in a second housing 15. that the structure 11 comprises or that comprises a third structure 13 of the watch sub-assembly 200, this second housing 15 constituting a stop, in particular radial.

[0107] More particularly, the second housing 15 surrounds a second structure 12 comprising such a limiting surface 120.

[0108] 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 bearing surface 16 which cooperates with a bore of revolution constituting the first housing 14.

[0109] The invention also relates to a movement 500 comprising at least one such watch sub-assembly 200.

[0110] The invention also relates to a watch 1000 comprising at least one such horological sub-assembly 200.

[0111] In a particular embodiment, the structure is made of ceramic, and comprises, at least in the vicinity of the surface of at least one housing 3, an encrustation of magnets or / and electrets, or / and ferromagnetic particles magnetizable.

[0112] In particular, the housing 3 is smooth.

[0113] In particular, the structure 1 comprises or constitutes a ferromagnetic shielding.

If we compare the invention to the embodiments of the prior art incorporating magnetic elements at the level of guides, the ETA 2894 caliber is known to use a magnet to brake a small second mobile, in the form of a 'friction to suppress the flutter; in this case the magnetic interaction is used only to dissipate the energy of the mobile, without ensuring the centering of the rotating mobile. The configuration of the shock absorber according to the invention differs in that: the relative position of the magnet and of the ferromagnetic part of the rotating body is invariant under rotation, thus avoiding torque variations due to this asymmetry; purely mechanical contacts have a minimum contact surface and give efficient tribology, thus minimizing energy dissipation, and therefore torque taking; in some variants, a mechanical stop intervenes only during shocks, while the magnetic field ensures the re-centering of the mobile after impact regardless of the amplitude of the shock: the mechanical and magnetic forces therefore intervene separately.

[0115] 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 angular displacements. The present invention aims at an exactly opposite function: the magnetic configuration is defined to impose a radial and / or axial holding / recentering 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 fig. 12, a fundamental characteristic of the invention is, in the case of axial retention, the cylindrical symmetry of the magnetic system.

[0116] The presence of magnetic attraction is one of the aspects characterizing the invention, in comparison with systems incorporating rather repulsive magnets.

[0117] 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 known precisely over 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 causing operating problems if the amplitude of the oscillation is too large. Whereas, in the context of the invention, magnetic force is, in most applications, used to press the shaft with a certain pre-stressing force against a mechanical stop. In normal operation, the component is therefore in a constant position fixed mechanically.

[0118] Known mechanisms do not exploit the magnetic properties of a component of which the magnetic parts are only appendages, precisely because 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 positioning centering, and where the positioning is very sensitive to tolerances (geometries of the magnets and retentive fields).

[0120] In fact, the dissipation of shock energy is not optimal with a magnetic system, which is highly conservative, and which forces the use of mechanical stops. In the invention, the recentering (radial for example in the case of Fig. 9) is a side effect of the anti-shock system (axial).

[0121] Figs. 10 and 11 show variants where the various magnetic fields present are not coaxial, and the interactions between components can in particular be oblique.

[0122] The operation of a system according to the invention, with magnets now in mechanical contact, on the other hand makes it possible to be insensitive (for positioning) to the tolerances of the magnet.

[0123] The main advantage of magnetic shock absorber for a shaft is the dependence of the restoring force on the displacement of the shaft, on the axial direction for example. As with traditional shock absorbers, a preload force, or a contact holding force in the case of magnetic shock absorbers, forces the component not to move during small impacts. Beyond this amplitude of shock, the return force of a traditional shock absorber increases with the distance of the component, due to the loading of the spring, while that of a magnetic shock absorber according to the invention decreases. with the distance from the component. This characteristic makes it possible to really decouple two different regimes: one where the shocks have low amplitudes, and the second with larger shock amplitudes, with a shock threshold value from which the energy is mechanically stored or dissipated. , by a stop for example.

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

[0125] The invention is distinguished by various advantages: to avoid torque variations due to possible asymmetry, we can construct the relative position of the magnet and of the ferromagnetic part of the invariant shaft under rotation; the purely mechanical contacts can be minimized, thanks to the magnetic or electrostatic axial retention, in particular in the configuration in repulsion without stop, and, in the case where these mechanical contacts are maintained, they present a minimal contact surface and give an effective tribology , with minimization of energy dissipation, and therefore of torque taking; these contacts can be as identical or larger than with a traditional friction spring, and therefore allow the energy dissipation to be exploited to damp the float of a needle or the like; in some variants of the invention, a mechanical stop intervenes only during significant shocks, while the magnetic field ensures 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 shocks: mechanical and magnetic forces therefore intervene separately; the magnetic or electrostatic configuration is defined to impose a radial and / or axial holding / recentering 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 variations of the invention is the cylindrical symmetry of the magnetic system around the pivot axis DA; the dependence on compliance with tolerances is less important than in the prior art; the problems associated with wear due to 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 significant shocks; the cooperation of the fields ensures a fine recentering after a shock; the highly elastic response of the 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 one motion, by magnetic or electrostatic forces; it is possible to treat shocks of different amplitudes in a different way, by making different components (or parts of components) work for dissipation. One can imagine an amplitude below which the magnetic force is exploited, and above which the dissipation is mechanical.

[0126] The horological embodiments in a magnetic variant function correctly with an axial field of 0.55 Tesla.

[0127] A particular embodiment relates to a steel shaft with a mass of 60 mg, maintained in contact by a magnet, in attraction, and with an axial field of 0.55 Tesla, the shaft has a diameter (for the part close to the 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 60 µm thick between the shaft and the magnet. A typical variation in magnetic potential between the mechanical stop and the contact in the operating position is 6 μJ for 0.1 mm of displacement, in particular in the case of this example. With a variation twice as large (0.12 J / m), we can for example achieve two potential stages, which occur during two different shock regimes (0–100 g and 100–200 g).

[0128] As regards the electrostatic variant, for similar applications, it is advisable to provide between 0.5 and 50 mC / m ^ 2 (a field of approximately 0.01–1 MV / m).

[0129] A system according to the invention can therefore be used to replace a mechanical friction spring. Any mechanical friction generated by this system is not necessarily a disadvantage, and can be exploited, including in the case of radiated support where friction against the chimney is high. Friction can therefore be exploited to dissipate the energy of the floating of a mobile such as a needle.

It is also possible to combine this mechanical friction due to the maintenance in contact, and braking of the eddy current type.

Claims (26)

Watchmaking sub-assembly (200) for a watch, comprising a main structure (100) and a shaft (10) pivotally movable 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 magnetic material or magnetic conductor, or respectively in electrified or electrostatically conductive material, and said main structure (100) having at least one polar mass (11; 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 axial and / or radial retention of said shaft (10), characterized in that at least one said polar mass (11; 12; 31; 32) is arranged to cooperate in axial attraction or repulsion and / or radial, along said axis pivoting member (DA) with at least one said surface (16; 18; 21; 22) for absorbing a shock e t return said shaft (10) to the service position after cessation of said shock. 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 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 main structure (100) comprises at least one pole mass (11; 12; 31; 32) arranged to create, close to at least one said surface (16; 18; 21; 22), at least one magnetic field, or respectively an electrostatic field, for radial holding of said shaft (10). 4. Watchmaking subassembly (200) according to one of claims 1 to 3, characterized in that at least one said magnetic field, or respectively electrostatic, tends to radially push said shaft (10) away from the walls of said housing ( 14; 15) and aligning said shaft (10) with said pivot axis (DA). 5. Watchmaking subassembly (200) according to one of claims 1 to 3, characterized in that at least one said magnetic field, or respectively electrostatic, tends to radially attract said shaft (10) to a wall of said housing (14). 15). 6. Watchmaking subassembly (200) according to one of claims 1 to 5, characterized in that said shaft (10) is braked axially along said pivot axis (DA) only by a magnetic potential, respectively electrostatic, varying the along the pivot axis (DA) and creating a resistive force resulting from the cooperation in attraction or repulsion between at least one said polar mass (11; 12; 31; 32) and at least one said surface (16; 18; 21; 22). 7. horological subassembly (200) according to claim 6, 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 ). 8. Watchmaking subassembly (200) according to one of claims 6 or 7, characterized in that said shaft (10) is braked axially along said pivot axis (DA) by said potential profile which forms at least one barrier magnetic field, respectively electrostatic, said barrier forming a virtual annular notch, arranged to brake or stop the stroke of said shaft along said pivot axis (DA). 9. Watchmaking subassembly (200) according to claim 8, 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. 10. sub-assembly watchmaker (200) according to claim 8 or 9, characterized in that said barriers are successive and have, along said pivot axis (DA), magnitudes of magnetic field, respectively electrostatic, which are increasing, since a service position of said shaft (10) towards a mechanical stop that comprises said main structure (100). 11. watch sub-assembly (200) according to claim 10, characterized in that said mechanical stop is paired with a magnetic stop or constitutes a magnetic stop. 12. Watchmaking subassembly (200) according to one of claims 1 to 11, characterized in that said shaft (10) is cylindrical 13. watch sub-assembly (200) according to one of claims 1 to 12, characterized in that at least one said housing (14; 15) of said main structure (100) is cylindrical. 14. Watchmaking subassembly (200) according to one of claims 1 to 13, characterized in that said main structure (100) comprises a lateral cutout (19) extending parallel to said pivot axis (DA) and dimensioned for allow insertion and extraction of said shaft (10). 15. watch sub-assembly (200) according to one of claims 1 to 14, characterized in that said main structure (100) comprises an end cutout (190) sized to allow the insertion and extraction of said shaft (10) along said pivot axis (DA). 16. Watchmaking subassembly (200) according to one of claims 1 to 15, characterized in that said main structure (100) comprises a first structure (11) comprising at least a first housing (14), at least in which said shaft (10) is pivotally movable, said first structure (11) 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) has 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 said first structure (11) 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 su magnetized or respectively electrified frontal face (18) that comprises said shaft (10). 17. watch sub-assembly (200) according to claim 16, characterized in that said field is a magnetic field and its intensity between said front surface (18) and said limiting surface (120) is greater than 0.55 Tesla . 18. watch sub-assembly (200) according to claim 16 or 17, characterized in that said at least one front surface (18) 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). 19. watch sub-assembly (200) according to one of claims 16 to 18, characterized in that said shaft (10) comprises two said end surfaces (18) opposite to each other, and in that said watch subassembly (200) comprises two said limiting surfaces (120) each arranged to attract or repel a said front surface (18). 20. watch sub-assembly (200) according to one of claims 16 to 19, characterized in that said shaft (10) comprises at least one said end surface (18) at a distal end along 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). 21. watch sub-assembly (200) according to claim 20, characterized in that said shaft (10) comprises a said end surface (18) at each of its distal ends along said shaft axis (AA). 22. watch sub-assembly (200) according to one of claims 16 to 21, characterized in that said shaft (10) comprises at least a first bearing (16) housed in said first housing (14) and having at least superficially a magnetized material or magnetic conductor, or respectively at least superficially comprising an electrostatic conductive material, said at least one first surface (16) being subjected, in said first housing (14), to said magnetic field, or respectively electrostatic field, generated by said first structure (11), and characterized in that said shaft (10) comprises at least a second bearing (17) housed in a second housing (15) that comprises said structure (11) or that comprises a third structure (13) of said watch sub-assembly (200) said second housing (15) constituting an abutment 23. watch sub-assembly (200) according to claim 22, characterized in that said second housing (15) surrounds a said second structure (12) having a said limiting surface (120). 24. watch sub-assembly (200) according to one of claims 16 to 23, 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 a first cylindrical bearing surface (16) which cooperates with a bore of revolution constituting said first housing (14). 25. Movement (500) comprising at least one horological subset (200) according to one of claims 1 to 24. 26. Watch (1000) comprising at least one watch sub-assembly (200) according to one of claims 1 to 24.