EP3882711B1 - Timepiece movement comprising an escapement provided with a magnetic system - Google Patents

Description

Technical area

The invention relates to watch movements comprising an escapement equipped with a magnetic system. More particularly, the invention relates to an escapement provided with a magnetic coupling system between an escape wheel and an anchor separate from the mechanical resonator, this anchor having an axis of rotation different from that of the mechanical resonator. As with a Swiss anchor, the anchor exhibits a reciprocating movement that is synchronous with, but different from, the periodic movement of the mechanical resonator. By magnetic escapement, we understand an escapement provided with magnets arranged partly on the anchor and partly on the escape wheel so as to generate a magnetic coupling between the anchor and the escape wheel.

Technology background

Various watch movements with magnetic escapements have already been proposed in patent applications. Concerning magnetic escapements comprising an anchor separated from the mechanical resonator, we can cite the document EP 2 894 522 and the document EP 3 208 667 . The first document proposes a combination of a magnetic escapement performing the function of the escapement alone in the normal operating range of the escapement, when the torque supplied to the escape wheel is less than a nominal torque, and of a mechanical escapement which takes over, ensuring the function of the escapement in addition to the magnetic escapement, when the torque applied to the anchor is greater than the nominal torque, particularly during a shock that the mechanical movement may undergo . The second document EP 3 208 667 describes more precisely a magnetic escapement with an anchor mechanically coupled to the mechanical resonator and magnetically to the escape wheel, the latter having two annular magnetic tracks formed by a planar and continuous magnetic structure, which defines magnetic potential energy ramps and magnetic barriers for at less a magnetic pallet of the anchor which is arranged to alternately follow sections of the two magnetic tracks, this magnetic pallet being formed by a magnet. With reference to Figure 20 of this document, it is proposed to arrange complementary mechanical stops between the anchor and the escape wheel, in order to ensure that the escapement does not stall in the event of an impact. These complementary stops are arranged so as to block the advance of the escape wheel when the magnet of a magnetic pallet of the anchor partially crosses a magnetic barrier following an impact.

The two aforementioned documents therefore propose mechanical means complementary to the magnetic coupling system between the escape wheel and the anchor to prevent the escape wheel from taking untimely additional steps in the event of shocks or other significant accelerations suffered by mechanical movement.

Summary of the invention

The inventors have highlighted a particular problem with magnetic escapements, which arises from the fact that the magnetic force is conservative. When a magnetic barrier of the rotating escape wheel abuts against a magnetic pallet of the anchor, we observe that the escape wheel undergoes a recoil and then an oscillation movement which can last for a relatively long time. To ensure constant and effective behavior of the magnetic escapement, it is advantageous that, before the anchor is rotated by the mechanical resonator during each alternation of the latter, the wheel escapement has stabilized substantially in a stopping position corresponding to a magnetic potential energy determined for a given torque of force which is applied to this escape wheel by a barrel via a train of the watch movement.

We therefore see that the oscillation movement undergone by the escape wheel, each time a magnetic barrier abuts against a magnetic pallet of the anchor, limits the operating frequency of the magnetic escapement and therefore the frequency of oscillation of the mechanical resonator. This is a disadvantage because a high oscillation frequency, for example greater than 4 Hz, makes it possible to better resist shocks and also to increase the quality factor of the mechanical resonator.

The present invention aims to provide a solution to this specific problem. To this end, the invention relates to a watch movement, as defined in claim 1, which comprises a mechanical resonator and an escapement which is associated with this mechanical resonator, the escapement comprising an escapement wheel and an anchor separated from the mechanical resonator and whose axis of rotation is different from that of the mechanical resonator. The mechanical resonator is coupled to the anchor in such a way that, when this mechanical resonator exhibits an oscillation, the anchor undergoes an alternating movement between two rest positions in which the anchor remains alternately during successive time intervals. The anchor comprises at least one magnetic pallet formed of a magnet and the escape wheel comprises a periodic magnetized structure which defines a plurality of increasing ramps of magnetic potential energy for said magnetic pallet, each of these increasing ramps of energy magnetic potential being arranged so that said magnetic pallet can climb it when the anchor is in a corresponding rest position among the two rest positions and a torque of force supplied to the escape wheel is equal to a torque of nominal force or included in a range of values which is intended for a normal operation of the watch movement. Then, said magnetic pallet and said plurality of increasing ramps of magnetic potential energy are arranged so that the anchor experiences a pulse of magnetic force in the direction of its movement, after said magnetic pallet has climbed any of said increasing ramps d magnetic potential energy, when the anchor tilts from one of the two rest positions having allowed this magnetic pallet to climb said any increasing ramp of magnetic potential energy towards the other rest position. In addition, the anchor includes at least one mechanical stop and the escape wheel includes projecting parts. Finally, the anchor and the escape wheel are arranged in such a way that, when said force torque is equal to said nominal force torque or presents a value in at least an upper part of said range of values and when the anchor presents said reciprocating movement, one of said projecting parts of the escape wheel undergoes at least one shock on a mechanical stop among said at least one mechanical stop after said magnetic pallet has climbed any one of said increasing ramps of magnetic potential energy following a tilting of the anchor into the rest position allowing this magnetic pallet to climb said any magnetic potential energy ramp, said at least one shock intervening so as to at least partially dissipate kinetic energy from the escape wheel acquired following audit changeover.

According to a preferred embodiment, the periodic magnetized structure further defines for the magnetic palette magnetic barriers located respectively following the increasing ramps of magnetic potential energy, each of these magnetic barriers being arranged so as to exert a magnetic force torque on the escape wheel, having a direction opposite to that of said torque of force supplied to this escape wheel, when the escape wheel is in an angular position of balance of the forces exerted on it while the magnetic palette is located at the top of the magnetic potential energy ramp which precedes the magnetic barrier considered, said magnetic force torque being greater than a maximum magnetic force torque generated by the magnetic potential energy ramp preceding the magnetic barrier considered before the escape wheel reaches said equilibrium angular position of the strengths.

Thanks to the characteristics of the invention, the hybrid escapement of the invention, that is to say of the magnetic and mechanical type, can generate, in normal operation of the watch movement, pulses of magnetic force supplied to the anchor in the direction of its movement during the tilting of this anchor between its two rest positions during its reciprocating movement, by an accumulation of magnetic potential energy between at least one magnetic pallet, carrying a magnet, and a periodic magnetized structure, carried by the escape wheel, by allowing the magnetic pallet to successively climb ramps of magnetic potential energy, which are formed respectively by arcuate portions of the periodic magnetized structure successively coupled to the magnetic pallet, while the anchor is in at least one of its two rest positions. Such magnetic coupling is generally obtained when the magnetic palette is successively superimposed on said arcuate portions. In addition, the non-fully elastic shocks provided between protruding parts of the escape wheel and at least one mechanical stop of the anchor, following each accumulation of magnetic potential energy between the anchor and the escape wheel, makes it possible to dissipate the kinetic energy presented by the escape wheel, so as to cushion at least a first rebound of the escape wheel and thus allow a relatively rapid stopping of the escape wheel, in particular before a next tilting of the anchor.

According to an advantageous variant, the escapement is arranged so that, following said shock and before a subsequent tilting of the anchor, the escape wheel stops momentarily in an angular stopping position which is said angular position of balance of forces.

According to a first case of the aforementioned advantageous variant, once the escape wheel is momentarily stopped in the angular stopping position, the projecting part bears against the mechanical stop in the angular stopping position.

According to a second case of the aforementioned advantageous variant, once the escape wheel is momentarily stopped in the angular stopping position, the projecting part is located at a distance from the mechanical stop in the angular stopping position, the protruding part and the mechanical stop thus not being in contact in this angular stopping position.

Brief description of the figures

• Les Figures 1A à 1F montrent partiellement un mouvement horloger selon un premier mode de réalisation de l'invention avec son échappement hybride dans des positions successives ;
• Les Figures 2A à 2F montrent partiellement un mouvement horloger selon un deuxième mode de réalisation de l'invention avec l'échappement hybride dans des positions successives ;
• La Figure 3 représente, pour un mouvement horloger muni d'un échappement ayant un système magnétique du type du deuxième mode de réalisation mais réalisé sans butée mécanique selon l'art antérieur, une courbe d'énergie potentielle magnétique pour chacune des deux positions de repos de l'ancre en fonction de l'angle de cette roue d'échappement, ainsi qu'un tracé simplifié de l'énergie potentielle magnétique d'une palette magnétique de l'ancre en fonction de l'angle de la roue d'échappement lors du fonctionnement normal du mouvement horloger ;

• La Figure 4 représente, pour le mouvement horloger de la Figure 3, le comportement précis de la roue d'échappement après qu'une palette magnétique de l'ancre a gravi une rampe d'énergie potentielle magnétique définie par la structure aimantée périodique ;
• La Figure 5 expose schématiquement, pour un mouvement horloger selon le deuxième mode de réalisation de l'invention, une première variante d'agencement et de fonctionnement de son échappement hybride à l'aide d'une courbe de l'énergie potentielle magnétique accumulée par une palette magnétique de l'ancre en fonction de l'angle de la roue d'échappement ;
• La Figure 6 expose schématiquement, pour un mouvement horloger selon le deuxième mode de réalisation de l'invention, une deuxième variante d'agencement et de fonctionnement de son échappement hybride à l'aide d'une courbe de l'énergie potentielle magnétique accumulée par une palette magnétique de l'ancre en fonction de l'angle de la roue d'échappement.

The invention will be described below in more detail using the appended drawings, given by way of non-limiting examples, in which:

• THE Figures 1A to 1F partially show a watch movement according to a first embodiment of the invention with its hybrid escapement in successive positions;
• THE Figures 2A to 2F partially show a watch movement according to a second embodiment of the invention with the hybrid escapement in successive positions;
• There Figure 3 represents, for a watch movement fitted with an escapement having a magnetic system of the type of the second embodiment but produced without a mechanical stop according to the prior art, a magnetic potential energy curve for each of the two rest positions of the anchor as a function of the angle of this escape wheel, as well as a simplified plot of the magnetic potential energy of a pallet magnetic of the anchor depending on the angle of the escape wheel during normal operation of the watch movement;

• There Figure 4 represents, for the watch movement of the Figure 3 , the precise behavior of the escape wheel after a magnetic pallet of the anchor has climbed a ramp of magnetic potential energy defined by the periodic magnet structure;
• There Figure 5 schematically presents, for a watch movement according to the second embodiment of the invention, a first variant of arrangement and operation of its hybrid escapement using a curve of the magnetic potential energy accumulated by a magnetic pallet of the anchor depending on the angle of the escape wheel;
• There Figure 6 schematically presents, for a watch movement according to the second embodiment of the invention, a second variant of arrangement and operation of its hybrid escapement using a curve of the magnetic potential energy accumulated by a magnetic pallet of the anchor depending on the angle of the escape wheel.

Detailed description of the invention

With the help of Figures 1A to 1F A first embodiment of a watch movement according to the invention will be described below.

The watch movement is of the mechanical type and includes a mechanical resonator 2, of which only the axis 4, the small plate 6 having a notch 8 and the pin 10 have been represented. The watch movement includes an escapement 12 which is associated with the mechanical resonator whose small plate and the pin are elements forming this escapement. The escapement 12 further comprises an escape wheel 16 and an anchor 14 which is a separate member of the mechanical resonator and whose axis of rotation is different from that of this mechanical resonator.

The anchor is formed, on the one hand, by a rod 20 ending in a fork 18 which comprises two horns 19a and 19b and, on the other hand, by two arms 24, 26 whose free ends respectively form two mechanical pallets 28 , 29 which define two mechanical stops. The two mechanical pallets respectively support two magnets 30, 32 which form two magnetic pallets of the anchor. We can therefore say that the anchor has hybrid, mechanical and magnetic vanes, each magnetic vane being associated with a mechanical vane. The mechanical resonator is coupled to the anchor in such a way that, when the mechanical resonator oscillates normally, this anchor undergoes an alternating movement, synchronized with the oscillation of the mechanical resonator, between two rest positions, defined by two limiting pins 21 and 22, in which the anchor remains alternately during successive time intervals which are greater than a third of the nominal period T0 of said oscillation.

The escape wheel 16 comprises a periodic magnetized structure 36 arranged on a disk 34 preferably made of non-magnetic material (not conducting magnetic fields). The structure 36 has portions 38 in the form of an arc defining increasing ramps of magnetic potential energy for the two magnetic pallets 30, 32 which each have an axial magnetization with a polarity opposite to that of the axial magnetization of the periodic magnetized structure . According to an advantageous variant, the periodic magnetized structure 36 is arranged so that its outer periphery is circular, the arc-shaped portions 38 of this magnetized structure having the same configuration and being arranged circularly around the axis of rotation of the wheel exhaust.

Generally speaking, each increasing ramp of magnetic potential energy is provided so that each of the two magnetic pallets can climb it when the anchor is in a given rest position among its two rest positions and a torque of force M _RE supplied to the escape wheel is substantially equal to a torque of nominal force (case of a mechanical movement equipped with a constant force system for driving the escape wheel) or included in a range of values provided to ensure the normal operation of the watch movement (case of a classic mechanical movement presenting a variable force torque applied to the escape wheel depending on the cocking level of the barrel or barrels if several are provided in series). The increasing ramps of magnetic potential energy are climbed, when the anchor undergoes an alternating movement between its two rest positions and when the force torque M _RE supplied to the escape wheel is equal to said nominal force torque or included in the range of values provided for this force torque in normal operation, successively by each of the first and second magnetic pallets when the anchor is respectively in its first and second rest positions, and alternately by these first and second magnetic pallets during movement alternative of the anchor. The two magnetic vanes and the increasing ramps of magnetic potential energy are arranged in such a way that the anchor can experience a pulse of magnetic force in the direction of its movement, after any of the two magnetic vanes has ascended any of said ramps. increasing magnetic potential energy, when the anchor tilts from the rest position corresponding to this any ramp of magnetic potential energy towards the other rest position.

The normal operation of a conventional mechanical movement (without a constant force system) is generally obtained, in particular to ensure the operation of the oscillator formed by the mechanical resonator and the escapement, with a force torque M _RE supplied to the wheel exhaust whose value is in a certain range of values allowing the maintenance of the mechanical resonator at a planned nominal oscillation frequency and the counting of the alternations of this oscillator. However, to have optimal operation with a watch movement having an escapement equipped with a magnetic coupling system between the escape wheel and the anchor, as described above, and to take full advantage of the advantages of such a magnetic coupling system, a hybrid system described below is provided within the framework of the invention.

The escape wheel further comprises projecting parts which are respectively associated with increasing ramps of magnetic potential energy. These projecting parts are formed, in the variant shown, by teeth 42 extending radially from a plate 40 secured to the escape wheel and located above the disc 34 carrying the magnetic structure 36. These teeth are located, in superposition, respectively at the end of the magnetized portions 38 which define the increasing ramps of magnetic potential energy, that is to say at the top of these increasing ramps. As explained below, the teeth 42 are arranged to cooperate with the mechanical pallets 28 and 29, which form mechanical stops for these teeth and therefore for the escape wheel. The teeth and mechanical vanes are formed by a non-magnetic material. In a general variant, the projecting parts are formed by teeth which extend in a general plane in which also extend the two mechanical pallets of the anchor respectively supporting the two magnets 30, 32 which are also located in the plane general. The figures only show a lower magnetized structure, located below the aforementioned general plane. However, in an advantageous variant, the escape wheel further comprises an upper magnetized structure, of the same configuration as the lower magnetized structure and supported by an upper disk preferably formed of a non-magnetic material. The lower and upper magnet structures together form the periodic magnet structure. They have the same magnetic polarity, opposite to that of the two magnets of the anchor, and are arranged on either side of the geometric plane in which these two magnets forming the two magnetic pallets are located, preferably at the same distance.

In the case of the first embodiment, the anchor and the escape wheel are arranged in such a way that, in normal operation (that is to say for a torque of force M _RE supplied to the escape wheel substantially equal to a nominal force torque or included in a range of values ensuring the normal operation of the watch movement and in particular correct step-by-step rotation of the escape wheel), one of the teeth of the escape wheel undergoes a shock on one of the two mechanical pallets of the anchor after the corresponding magnetic pallet has climbed any of the increasing ramps of magnetic potential energy following a tilting of the anchor. This shock occurs so as to at least partially dissipate kinetic energy from the escape wheel acquired following said tilting. This shock is therefore not a hard shock (totally elastic shock). In a practical case, at least a first shock is not soft (totally inelastic shock), but it is partially elastic so that the escape wheel experiences at least one rebound after this first shock. Thus, the exhaust of the invention is called 'hybrid exhaust'.

In an advantageous variant of the first embodiment, the hybrid escapement is arranged so that the escape wheel momentarily stops in an angular stopping position after any one of the teeth 42 has abutted against any one of the two mechanical pallets and before a subsequent tilting of the anchor. In normal operation and once the escape wheel is momentarily stopped in any angular stopping position of the escape wheel, a tooth 42 presses against a mechanical stop formed by one or the other of the two mechanical pallets.

To minimize the immobilization time of the escape wheel, the shocks are at least partially inelastic so that the anchor and/or the escape wheel, or even the cog that drives it, absorbs and dissipates the shock. kinetic energy of this escape wheel with each shock. We will notice that the greater the absorption of kinetic energy during an impact between a tooth and a mechanical pallet, the better the damping of the oscillation occurring after the first impact will be. Note that the magnetic forces are conservative, so that only the friction exerted on the escape wheel, or even the cog that drives it, and the shocks between a tooth and a mechanical pallet can absorb energy. kinetic and therefore dampen an oscillation generated following said first shock after the escape wheel has stored magnetic potential energy in the hybrid escapement.

To illustrate the operation of the hybrid exhaust of the first embodiment, the Figures 1A to 1F show various successive stages of an oscillating mechanical resonator 2 and a hybrid exhaust 12. At the Figure 1A , the anchor 14 is stationary in a first rest position and the balance of the resonator rotates towards its neutral position (minimum mechanical potential energy). The magnet 30, forming the first magnetic palette, is located at the top of an increasing ramp of magnetic potential energy (superposition of the magnet with part of a magnetized portion 38 having a relatively large width). When the escape wheel 16 is in an angular stopping position, once the escape wheel is momentarily stopped, and the anchor in its first rest position, a tooth 42 rests against a mechanical stop formed by the first mechanical pallet 28, this tooth pressing against an interior surface of this first mechanical pallet. We are therefore in a situation of balance of forces exerted on the escape wheel.

In the advantageous variant shown, each magnetized portion 38 has a monotonically increasing width and its end part, which has the greatest widths, extends beyond the magnet associated with the mechanical pallet in the positive angular direction (the wheel escapement rotating step by step in the negative angular direction) while this mechanical pallet presses against a tooth, so that the escape wheel undergoes a magnetic force of positive direction and therefore a positive magnetic force torque which reduces, for the force torque supplied to the escape wheel, the tangential mechanical force exerted by the tooth on the mechanical pallet and therefore the force normal to the surface contact of this mechanical pallet. In particular, the width of the magnetized portions increases, over their entire useful length, linearly as a function of the central angle. Thus, the accumulation of magnetic potential energy is linear as a function of the angle of rotation of the escape wheel for each of the increasing ramps of magnetic potential energy and the magnetic force exerted on the escape wheel is constant when a magnetic pallet climbs this increasing ramp to an angular stopping position of the escape wheel in which one of its teeth is in contact with the corresponding mechanical pallet, the same constant magnetic force then being exerted still on the escape wheel in this angular stopping position.

Thanks to the characteristics of this advantageous variant, the static friction and the dynamic friction between the tooth and the mechanical pallet are reduced, so that the torque required for the next tilting of the anchor is less. Thus, the magnetic system of the hybrid escapement makes it possible, on the one hand, to accumulate magnetic potential energy in the escapement to generate pulses of magnetic force applied to the anchor and, on the other hand, to reduce the release torque that the mechanical resonator must provide during each tilting of the anchor. In other words, reducing friction makes it possible to reduce energy losses due to mechanical contact between the anchor and the escape wheel before each tilting of the anchor between its two rest positions.

There Figure 1B shows a stage in the operation of the hybrid escapement where the anchor has just been released by the pin 10 of the mechanical resonator 2 and switches between its first rest position and its second rest position. During this movement of the anchor, the magnet 30 moves radially (relative to the escape wheel) and passes from a state superimposed on the magnetized portion 38, corresponding to a state of high magnetic potential energy, to a state not superimposed on this magnetized portion corresponding to a state of low magnetic potential energy; which generates a pulse of magnetic force applied to the magnetic pallet (magnet 30) and thus the anchor experiences a torque of magnetic force, so that the anchor then becomes a driver for the mechanical resonator. There Figure 1C shows the anchor in its second rest position just after a tilt. The escape wheel 16 then turns one step in the negative direction and the magnet 32 climbs an increasing ramp of magnetic potential energy thanks to the torque supplied to the escape wheel. There Figure 1D shows a rebound of the escape wheel after a first impact of a tooth 42 on the mechanical pallet 29 while the mechanical resonator is in an angular position close to its amplitude. There Figure 1E shows a stage corresponding to that of the Figure 1A but for the anchor stationary in its second rest position. In the angular stopping position of the escape wheel shown in Figure 1E , a tooth 42 presses against an exterior surface of the second mechanical pallet 29. Finally, the Figure 1F shows a coupling between the mechanical resonator and the anchor during which a magnetic force pulse again intervenes, as in the Figure 1B but applied to the second pallet so that the resulting magnetic force torque is in the opposite direction to that of this Figure 1B .

With the help of Figures 2A to 2F And 3 has 6 , we will describe various variants of a second embodiment of a watch movement according to the invention (note that the figures 3 and 4 are given for explanatory purposes, but do not relate to variants of the invention). The references already described previously will not be described again in detail.

The second embodiment is generally distinguished from the first embodiment by the fact that the periodic magnetized structure 36A further defines for each of the two magnetic pallets magnetic barriers 50 located respectively following the increasing ramps of magnetic potential energy defined by the magnetized portions 38A, these magnetic barriers being formed in particular by magnetized areas 50 of the structure 36A whose radial dimension is substantially equal to or greater than the longitudinal dimension of each of the two magnets 30 and 32 forming the magnetic pallets of the anchor. Each magnetic area/magnetic barrier is arranged so as to exert a magnetic force torque on the escape wheel 16A, having a direction opposite to that of said force torque supplied to this escape wheel, when this escape wheel is in an angular position of balance of the forces exerted on it while one or the other of the two magnetic pallets is located at the top of the magnetic potential energy ramp / at the widest end of the portion magnetized 38A which precedes the magnetic barrier / the magnetic area 50 considered. The arrangement of the magnetic barriers is designed so that the magnetic force torque exerted on the escape wheel in each force balance angular position is greater than a maximum magnetic force torque generated by the escapement ramp. magnetic potential energy / the magnetized portion 38A preceding the magnetic barrier considered before the escape wheel reaches the angular position of balance of forces.

Before describing in more detail various variants of the second embodiment, we will describe using the Figures 3 and 4 the operation of a watch movement equipped with a magnetic escapement having a magnetic system of the type of the second embodiment but produced without a mechanical stop. By 'type of the second embodiment', we understand in particular an escapement provided with a magnetic system which comprises, on the one hand, a periodic magnetized structure which is carried by the wheel exhaust and presenting, in a lower plane and/or an upper plane, a single circular magnetic track formed by a succession of similar magnetized portions (in a reference system “r, θ” with r = radius and θ = angle at center of the wheel) separated by magnetic areas and, on the other hand, two magnetic pallets carried by the anchor which are alternately coupled with the periodic magnetized structure. As the exhaust affected by the Figures 3 and 4 is purely magnetic, the magnetized areas must form relatively large magnetic barriers to ensure the desired synchronization between the reciprocating movement of the anchor and the step-by-step rotation of the escape wheel and also to prevent the escapement from stalling too quickly in the event of accelerations that the watch movement could undergo. Thus, the magnetic potential energy peaks formed here by the magnetized areas for each magnetic pallet are greater than those which are necessary in the second embodiment of the invention and which appear in the Figures 5 and 6 , which will be described later.

To Figures 3 and 4 , for each of the two rest positions of the anchor, a curve 54, 56 of magnetic potential energy EP _M , defined by the periodic magnetized structure of the escape wheel for each of the two magnetic pallets of the anchor, in function of the angle θ of this escape wheel is given. The two curves 54 and 56 are similar, but phase shifted by approximately 180° and they each define a magnetic period PM. Each curve presents increasing ramps of magnetic potential energy 60, 60A and magnetic barriers 62, 62A each defined by a peak of magnetic potential energy. To the Figure 3 , a simplified plot 58 of the magnetic potential energy EP _M of a magnetic vane (30 or 32) of the anchor (14) as a function of the angle θ of the escape wheel, during normal operation of the watch movement, is represented. The general behavior is as follows: In a first rest position of the anchor, a first magnetic pallet climbs a ramp 60 up to a certain height of magnetic potential energy then that the escape wheel rotates continuously, then the escape wheel undergoes an oscillation in a 'free' oscillation zone ZO _L around a certain balance point of forces PE _M (shown more precisely in Figure 4 ) due to the magnetic barrier which succeeds each ramp, and finally the first magnetic pallet undergoes, under the action of the oscillating mechanical resonator, a drop in magnetic potential energy 64 during the next tilting of the anchor into its second position rest. This drop in magnetic potential energy corresponds to a pulse of magnetic force applied to the anchor. During the next step, while the first magnetic pallet is outside the magnetic structure (in superposition) and then has substantially zero magnetic potential energy, the second magnetic pallet in turn climbs a ramp 60A due to the fact that it is superimposed on the magnetic structure. During the next tilting of the anchor, it is the second magnetic pallet which undergoes a pulse of magnetic force and the first magnetic pallet climbs, if necessary, a small step of magnetic potential energy. Thus, the energy transmitted to the anchor at each step of the escape wheel corresponds to the difference between the fall and the step that each of the two magnetic pallets undergoes alternately, the energy transmitted per magnetic period PM corresponding to twice that of this difference.

To the Figure 4 are indicated some magnetic forces generated by a magnetic pallet on the periodic magnetized structure of the escape wheel as a function of the angular position of this wheel. The magnetic forces present are given by the gradients of the magnetic potential energy curve 54. Thus, each ramp 60, 60A generates a magnetic force G1 which corresponds to a magnetic force torque on the escape wheel having an intensity lower than the force torque supplied to the escape wheel when this force torque is equal to the torque of nominal force or within the range of values expected in normal operation. It will be noted that in a variant where the two magnetic pallets are coupled simultaneously and alternately to two magnetic tracks during the accumulation of magnetic potential energy, it is twice the aforementioned magnetic force torque that must be considered. In the absence of mechanical stops, as indicated in Figure 4 , each magnetic barrier 62, 62A brakes the escape wheel in an angular zone ZF _M of magnetic braking which depends on the torque supplied to the escape wheel. As the magnetic force is conservative, the kinetic energy of the escape wheel can only be dissipated by friction in the bearings of the escape wheel and possibly in the gear train which drives it. Thus, the escape wheel undergoes a 'free' oscillation in an angular zone of 'free' oscillation ZO _L (that is to say without absorption of energy by a mechanical stop) around a point of balance of forces PE _M where the torque of force supplied to the escape wheel is compensated by the torque of magnetic force (without considering the friction forces) which is generated by the magnetic force G2 (gradient of curve 54 at the position angular PE _M ). The point of balance of forces PE _M therefore corresponds to a determined angular position of the escape wheel in which it can be stationary in a stable manner without contact between this escape wheel and the anchor. The balance point of forces PE _M and the angular zone of 'free' oscillation ZO _L vary according to the torque supplied to the escape wheel. The intensity of the magnetic force G2 is necessarily greater than the magnetic force G1. It will also be noted that each magnetic barrier, in the embodiment described in Figures 3 and 4 , corresponds in curves 54 and 56 to a peak of potential energy presenting a wall with a relatively steep slope G3.

The magnetic escapement described with reference to Figures 3 and 4 presents an operational problem due to oscillation of the escape wheel after a magnetic potential energy ramp has been climbed by a magnetic vane. As explained, there is little dissipation of the kinetic energy of the escape wheel (arising from the difference in intensity between G1 and G2) arriving against a magnetic barrier, so that this oscillation has an amplitude which can be quite important and low depreciation. On the one hand, if the anchor tilts while the escape wheel is still oscillating, the drop in magnetic potential energy 64 is variable and therefore poorly defined. We therefore do not have constant maintenance of the mechanical resonator, which is a disadvantage. On the other hand, if we have to wait until the oscillation of the escape wheel is sufficiently damped to be negligible, then the frequency of the reciprocating movement of the anchor must be limited and therefore also the frequency of oscillation of the mechanical resonator. This is also a disadvantage. The hybrid exhaust of the invention solves this problem.

The arrangement of magnetic barriers 50 in combination with the teeth 42 of the escape wheel in the second embodiment of the invention has the consequence that various variants can arise for a given hybrid anchor, with its mechanical pallets and pallets magnetic, depending on the relative angular positioning between each tooth and the corresponding magnetic barrier and also depending on the type of drive of the escape wheel.

With reference to Figures 5 and 6 , we will describe two possible variants for a watch movement, according to the second embodiment of the invention, provided with a system for driving the escape wheel with constant force Fc, the force torque M _RE ^ct supplied to the escape wheel also being constant. To Figures 5 and 6 are represented two curves 70 and 72 of magnetic potential energy EP _M defined by the periodic magnetized structure 36A of the escape wheel 16A respectively for two hybrid pallets of a hybrid anchor 14A, which is similar to the anchor 14 represented in there Figure 2A but with two hybrid palettes presenting a simplified and symmetrical shape. Curves 70, 72 are general curves, slightly schematized to simplify the drawing without harming the physical principles exposed and mathematical relationships given subsequently. These curves each define, for each magnetic period PM, increasing ramps 60, 60A with a gradient characteristic G1, similar to those described with reference to Figures 3 and 4 , and magnetic barriers 74, 74A lower than the magnetic barriers 62, 62A defined by a periodic magnetized structure provided without the protruding stopping parts. The magnetic areas forming the magnetic barriers 74, 74A can thus be angularly narrower; which makes it possible in particular to increase the number of steps per revolution for the escape wheel. The plot 68 of the magnetic potential energy EP _M of the magnetic pallet 31 as a function of the angle θ of the escape wheel, during normal operation of the hybrid escapement, is also represented in Figures 5 and 6 . We can see that it is similar to the simplified route 58 of the Figure 3 .

A hybrid pallet, which is formed of a mechanical pallet 28A supporting a magnet 31 which defines a magnetic pallet associated with the curve 70, is represented along the axis of the angular position θ of the escape wheel while this the latter is in a stopping position, after absorption of its kinetic energy following an accumulation of magnetic potential energy and before a next tilting of the anchor. The mechanical pallet 28A has a half-width DL which corresponds to the distance between the center of mass of the magnet 31 and the abutment surface defined by this mechanical pallet for the teeth 42 of the escape wheel 16A.

The two variants described are part of a general mode of the invention in which the hybrid exhaust is arranged in such a way that, following an impact of a mechanical pallet against any of the protruding parts of the wheel escape and before a next tilting of the anchor, the escape wheel stops in an angular stopping position which is an angular position of balance of the forces present. To Figures 5 and 6 , the angular position of balance of forces PE _M , in the (fictitious) absence of stopping teeth at the escape wheel, and the magnetic braking zone ZF _M which would intervene in the fictitious case without the teeth 42 are indicated, as explained with reference to the Figures 3 and 4 .

In the first variant shown in Figure 5 and also in the second variant shown in Figure 6 , the anchor 14A and the escape wheel 16A are arranged so that one of the teeth 42 of the escape wheel experiences an impact on a mechanical pallet of the anchor, in particular the mechanical pallet 28A, after the pallet corresponding magnetic, in particular the magnet 31, has climbed any of the increasing ramps of magnetic potential energy, in particular a ramp 60. As in the first embodiment, this shock occurs so as to at least partially dissipate a kinetic energy of the escape wheel. Indeed, the teeth of the escape wheel are designed to absorb the kinetic energy of this escape wheel, after an accumulation of magnetic potential energy in the escapement for a next maintenance pulse of the mechanical resonator, and limit a terminal oscillation during each step of its step-by-step rotation.

Moreover, in the first variant of the Figure 5 , the anchor 14A and the escape wheel 16A are arranged so that, after at least a first shock between a mechanical pallet and a tooth, the escape wheel stops, before the anchor swings again to the during its reciprocating movement between its two rest positions, to an angular stopping position, which is by definition an angular position of balance of forces, in which the tooth 42 having suffered said impact presses against the mechanical pallet. Thus, in this first variant, the angular stopping position PE _D is defined by a tooth bearing against a mechanical pallet. Thanks to this feature, the angular stopping positions are precisely defined by the protruding parts and the magnetic force pulses which are periodically supplied to the anchor present a constant intensity. On the other hand, this first variant generates a small loss of energy because of the friction between the tooth and the mechanical pallet when the anchor tilts. The stopping angular position PE _D is upstream of the angular position PE _M. The magnetic force in each position PE _D , which corresponds to a balance of forces present, is given by the gradient G4 of curve 70, respectively 72, at this position PE _D. The situation corresponding to the first variant is characterized by a distance PB1 between the angular position PE _M and the contact point of the tooth 42 which is less than the half-width DL of the mechanical pallet 28A (PB1 < DL).

The second variant is distinguished from the first variant by the fact that the angular stopping position is the angular position PE _M , given that, in this second variant, the anchor 14A and the escape wheel 16A are arranged so that, after at least a first shock between a mechanical pallet and a tooth, the escape wheel stops, before the anchor tilts again during its reciprocating movement between its two rest positions, at an angular position stop in which said tooth is located at a distance from said mechanical pallet, this angular stop position then corresponding to the angular position PE _M of balance of forces without mechanical stop described previously, in which the magnetic force torque of the system magnetic of the escapement and the constant force torque M _RE ^ct supplied to the escape wheel have the same intensity (excluding friction forces). For said first shock according to the invention to take place, the anchor and the escape wheel are arranged so that the distance DB between the contact surface of said mechanical pallet and the contact point of said tooth is less than one angular distance defined by the magnetic braking zone ZF _M (DB < ZF _M ). The magnetic force in each angular position PE _M , which corresponds to an angular stopping position for the escape wheel, is given by the gradient G5 of curve 70, respectively 72, at this position PE _M. Note that the value of the gradient G5 is necessarily greater than that of the gradient G4 occurring in the first variant. The situation corresponding to the second variant is characterized by a distance PB2 between the angular position PE _M and the contact point of the tooth 42 which is greater than the half-width DL of the mechanical pallet 28A (PB2 > DL). Note that the angular position PE _M is determined by the constant force torque M _RE ^ct .

In the case of a classic escape wheel drive, i.e. without a constant force system, a greater number of variants can be distinguished. To present them analytically, we consider a general case where, in normal operation of the watch movement in question, the range of values PV _M for the force torque M _RE supplied to the escape wheel extends between a minimum value M _RE ^min and a maximum value M _RE ^max greater than the minimum value: PVnn = [ M _RE ^min ; M _RE ^max ]. The value range PV _M is composed of a lower part PI1 _M and an upper part PS1 _M or, alternatively, a lower part PI2 _M and an upper part PS2nn. In addition, the upper part PS2 _M is composed of an upper zone ZS _PS and a lower zone ZI _PS (PS2 _M = ZI _PS + ZS _PS ), the complementary part PC _M to the upper zone ZS _PS in the range of values PV _M (PV _M = PC _M + ZS _PS ) being equal to the lower zone ZI _PS added to the lower part PI2 _M (PC _M = PI2 _M + ZI _PS ). The distance between the contact surface of the mechanical blade considered and the contact point of the tooth considered is called `DB', this distance being a function of the force torque M _RE . The magnetic braking zone, in the fictitious absence of stopping teeth on the escape wheel, is called 'ZF _M ', the extent of this zone being a function of the force torque M _RE .

In a main variant, for the entire range of values PV _M of the torque M _RE at least one first shock is provided between any of the teeth 42 of the escape wheel and any mechanical pallet of the anchor, in particular the mechanical palette 28A, after the corresponding magnetic palette has climbed one of the increasing ramps of magnetic potential energy associated with this corresponding magnetic palette and the tooth considered. This first main variant is expressed by the relationship: ZF _M (M _RE ^min ) > PB (M _RE ^min ) - DL.

Three variants can be distinguished within the main variant. In a first secondary variant, it is provided for the entire range of values PV _M of the force torque M _RE that the escape wheel stops, after said at least one first shock and before a subsequent tilting of the anchor, at an angular stop position in which the tooth having undergone said at least one first shock presses against the mechanical pallet. This first secondary variant is expressed by the mathematical relationship: PB (M _RE ^min ) < DL. In a second secondary variant, it is provided for the entire range of values PV _M of the force torque M _RE that the escape wheel stops, after said at least one first shock and before a subsequent tilting of the anchor, at an angular stop position in which the tooth having undergone said at least one first shock is located at a distance from the mechanical pallet against which it has abutted. This second secondary variant is expressed by the mathematical relationship: PB (M _RE ^max ) > DL. A mixed variant can also be distinguished within the framework of the main variant. In this mixed variant, for a lower part PI1 _M of the range of values PV _M , the tooth having undergone said at least one first shock is located at a distance from the mechanical pallet against which it has abutted when the escape wheel is momentarily immobilized. On the other hand, for an upper part PS1 nn of the range of values PV _M , the tooth having undergone said at least one first shock presses against the mechanical pallet against which it has abutted when the escape wheel is momentarily immobilized. This mixed variant can be expressed by the following two relations: PB (PI1 _M ) >DL; PB (PS1 _M ) < DL.

In a particular variant, only for an upper part PS2 _M of the range of values PV _M of the force torque M _RE occurs at least one shock between any one of the teeth 42 of the escape wheel and any mechanical pallet of the anchor, in particular the mechanical pallet 28A, after the corresponding magnetic pallet has climbed one of the increasing ramps of magnetic potential energy associated with this corresponding magnetic pallet and the tooth considered. On the other hand, for a lower part PI2 _M of the range of values PV _M of the force torque M _RE , no shock occurs between one of the teeth 42 of the escape wheel and a mechanical pallet of the anchor after the magnetic pallet corresponding has climbed one of the increasing ramps of magnetic potential energy associated with this corresponding magnetic palette. This particular variant can be expressed by the following two relationships: $${\mathrm{ZF}}_{\mathrm{M}}\left({\mathrm{PS2}}_{\mathrm{M}}\right)>\mathrm{P.B.}\left({\mathrm{PS2}}_{\mathrm{M}}\right)-\mathrm{D.L.}\mathrm{And}{\mathrm{ZF}}_{\mathrm{M}}\left({\mathrm{PI2}}_{\mathrm{M}}\right)<\mathrm{P.B.}\left({\mathrm{PI2}}_{\mathrm{M}}\right)-\mathrm{D.L.}.$$

We can still distinguish two variants within the framework of the particular variant presented above. In a specific variant, it is provided for the entire range of values PV _M of the force torque M _RE that the escape wheel stops, after said at least one shock and before a next tilting of the anchor, at a angular stopping position in which the tooth having suffered said at least one first shock is located at a distance from the mechanical pallet against which it abutted. This specific variant is expressed, as for the second secondary variant in the context of the first main variant, by the relationship: PB (M _RE ^max ) > DL. In a mixed variant provided within the framework of the particular variant considered, the tooth having suffered said at least one impact presses, once momentarily stopped in the angular stopping position, against the mechanical pallet against which it abutted when the force torque M _RE supplied to the escape wheel has a value in an upper zone ZS _PS of said upper part PS2 _M of the range of values PV _M. On the other hand, in the lower zone ZI _PS of the upper part PS2 _M , the escape wheel stops, after said at least one shock and before a subsequent tilting of the anchor, at an angular stopping position in which the tooth having suffered said at least one impact is located at a distance from the mechanical pallet against which it abutted. Thus, for the complementary part PC _M to the upper zone ZS _PS in the range of values PV _M , no tooth abuts against a mechanical pallet in the angular stopping position. This mixed variant can be expressed by the following two relationships: PB (PC _M ) >DL; PB (ZS _PS ) < DL.

There Figure 2A shows a stage of operation of the hybrid escapement 12A of the second embodiment where the anchor 14 is in one of its two rest positions and the escape wheel 16A is stationary. THE Figures 2A to 2F relate to a variant of operation in which the torque supplied to the escape wheel does not allow a tooth 42 to bear against a mechanical pallet 28 or 29 when it is stopped after having accumulated potential energy magnetic, by climbing a ramp of magnetic potential energy, and before a next tilting of the anchor. However, the distance between the contact point of the tooth 42 and the contact surface of the mechanical vane 28 at the Figure 2A , respectively 29 at the Figure 2F is advantageously low.

To the Figure 2B , the anchor has just been released by the pin 10 of the mechanical resonator 2 and it switches between its first rest position and its second rest position. During this movement of the anchor, the magnet 30 moves radially and passes from a state superimposed on the magnetized portion 38A, corresponding to a state of high magnetic potential energy, to a state not superimposed on this magnetized portion corresponding to a state of low magnetic potential energy; which generates a pulse of magnetic force applied to the magnetic pallet (magnet 30) and thus the anchor undergoes a force torque, so that the anchor then becomes a driver for the mechanical resonator. There Figure 2C shows the anchor in its second rest position just after a tilt. The escape wheel 16A then turns one step in the negative direction and the magnet 32 climbs an increasing ramp of magnetic potential energy (magnetized portion 38A) thanks to the torque supplied to the escape wheel.

There Figure 2D shows a first shock between a tooth 42 and the mechanical pallet 29 after the escapement 12A, formed of the anchor 14 and the escapement wheel 16A, has climbed an increasing ramp of magnetic potential energy. There Figure 2E shows a rebound of the escape wheel after the first impact of a tooth 42 on the mechanical pallet 29 shown in the previous figure. Finally, the Figure 2F shows a stage corresponding to that of the Figure 2A , but with the anchor 14 stationary in its second rest position.

Claims (12)

1. Horological movement comprising a mechanical resonator (2) and an escapement (12, 12A) which is associated with this mechanical resonator, the escapement comprising an escapement wheel (16, 16A) and a pallet assembly (14, 14A) separate from the mechanical resonator and of which the axis of rotation is different from that of the mechanical resonator; the mechanical resonator being coupled with the pallet assembly such that, when this mechanical resonator has an oscillation, the pallet assembly is subject to an alternating movement between two rest positions wherein the pallet assembly remains alternately during successive time intervals; the pallet assembly comprising at least one magnetic pallet-stone formed of a magnet (30, 31, 32) and the escapement wheel comprising a periodic magnetised structure (36, 36A) which defines a plurality of increasing gradients of magnetic potential energy (38, 38A) for said magnetic pallet-stone, each of these increasing gradients of magnetic potential energy being configured such that said magnetic pallet-stone can climb it when the pallet assembly is in a corresponding rest position of the two rest positions and that a force torque supplied to the escapement wheel corresponds to a normal operation of the horological movement, this force torque being equal to a nominal force torque or within a range of values which is selected for the normal operation of the horological movement, said magnetic pallet and the periodic magnetised structure being arranged such that the pallet assembly is subject to a magnetic force impulse in the direction of the alternating movement thereof, after said magnetic pallet-stone has climbed any one of said increasing gradients of magnetic potential energy, when the pallet assembly tips from one of the two rest positions having enabled this magnetic pallet-stone to climb said any one increasing gradient of magnetic potential energy to the other rest position;
   characterised in that the pallet assembly comprises at least one mechanical banking (28, 28A, 29) and the escapement wheel comprises protruding parts (42); and in that the pallet assembly and the escapement wheel are arranged such that, when said force torque is equal to said nominal force torque or has a value within at least an upper part of said value range and when the pallet assembly has said alternating movement, one of said protruding parts of the escapement wheel is subjected to at least one shock on a mechanical banking of said at least one mechanical banking after said magnetic pallet-stone has climbed any one of said increasing gradients of magnetic potential energy following a tipping of the pallet assembly in the rest position enabling this magnetic pallet-stone to climb this any gradient of magnetic potential energy, said at least one shock occurring so as to dissipate at least partially a kinetic energy of the escapement wheel acquired following said tipping.
2. Horological movement according to claim 1, characterised in that said shock is partially elastic such that the escapement wheel (12, 12A) has a rebound following this shock.
3. Horological movement according to claim 1 or 2, characterised in that the pallet assembly (14) and the escapement wheel (16) are arranged such that, during said normal operation of the horological movement, one of said protruding parts (42) of the escapement wheel is subjected to at least one shock on said mechanical banking of the pallet assembly after said magnetic pallet-stone has climbed any one of said increasing gradients of magnetic potential energy following a tipping of the pallet assembly in the rest position enabling the magnetic pallet-stone to climb this any gradient of magnetic potential energy; and in that the escapement is arranged such that the escapement wheel is immobilised momentarily in an angular stopping position following said shock and before a subsequent tipping of the pallet assembly, said protruding part pressing against the mechanical banking once the escapement wheel has momentarily stopped in the angular stopping position.
4. Horological movement according to claim 1 or 2, characterised in that the periodic magnetised structure (36A) furthermore defines for the magnetic pallet-stone magnetic barriers (50) located respectively after the increasing gradients of magnetic potential energy (38A), each of these magnetic barriers being arranged so as to exert a magnetic force torque on the escapement wheel, having an opposite direction to that of said force torque supplied to this escapement wheel, when the escapement wheel is in an angular equilibrium position of the forces exerted thereon while the magnetic pallet-stone is located at the magnetic potential energy gradient preceding the magnetic barrier in question, said magnetic force torque being greater than a maximum magnetic force torque induced by the magnetic potential energy gradient preceding the magnetic barrier in question before the escapement wheel reaches said angular equilibrium position of the forces.
5. Horological movement according to claim 4, characterised in that the escapement (12A) is arranged such that, following said shock and before a subsequent tipping of the pallet assembly, the escapement wheel is momentarily immobilised in an angular stopping position which is said angular equilibrium position of the forces.
6. Horological movement according to claim 5, characterised in that, once the escapement wheel has momentarily stopped in the angular stopping position, said protruding part subjected to said shock presses against said mechanical banking when the force torque supplied to the escapement wheel is equal to the nominal force torque or has a value within at least an upper zone of said upper part of said range of values.
7. Horological movement according to claim 5, characterised in that, during said normal operation and once the escapement wheel has momentarily stopped in the angular stopping position, said protruding part subjected to said shock presses against said mechanical banking.
8. Horological movement according to claim 5, characterised in that, during said normal operation and once the escapement wheel has momentarily stopped in the angular stopping position, said protruding part subjected to said shock is located at a distance from said mechanical banking, this angular stopping position corresponding substantially to an equilibrium position between said magnetic force torque and said force torque supplied to the escapement wheel.
9. Horological movement according to any one of the preceding claims, wherein said magnetic pallet-stone (30) is a first magnetic pallet-stone and said magnetic pallet-stone (28) is a first mechanical banking associated with the first magnetic pallet-stone; characterised in that the pallet assembly comprises a second magnetic pallet-stone (32) and a second mechanical banking (29) associated with this second magnetic pallet-stone, said periodic magnetised structure (36A) and the pallet assembly (14) being arranged such that said plurality of increasing gradients of magnetic potential energy (38, 38A) are also defined for the second magnetic pallet-stone, these increasing gradients being capable of being climbed, when the force torque supplied to the escapement wheel is equal to said nominal force torque or comprised within said range of values selected for said normal operation of the horological movement, successively by each of the first and second magnetic pallet-stones, when the pallet assembly is periodically in a first rest position, respectively in a second rest position of said two rest positions, and alternately by these first and second magnetic pallet-stones during the alternating movement of the pallet assembly; in that said second magnetic pallet-stone (32) and the plurality of increasing gradients of magnetic potential energy are arranged such that the pallet assembly is subject to a magnetic force impulse in the direction of the movement thereof, after the second magnetic pallet-stone has climbed any one of said increasing gradients of magnetic potential energy, when the pallet assembly tips from the second rest position to the first rest position; in that each increasing gradient of said plurality of increasing gradients of magnetic potential energy is associated with a different protruding part of said protruding parts; and in that the pallet assembly and the escapement wheel are arranged such that, when the pallet assembly exhibits said alternating movement and said force torque is equal to said nominal force torque or within said at least an upper part of said range of values and after the first or second magnetic pallet-stone has climbed any one of said increasing gradients of magnetic potential energy following a tipping of the pallet assembly in the first or second corresponding rest position, the protruding part of the escapement wheel associated with said any one of said increasing gradients of magnetic potential energy is subject to at least one shock on said first or second mechanical banking of the pallet assembly, this shock occurring so as to dissipate at least partially the kinetic energy of the escapement wheel following this tipping.
10. Horological movement according to claim 9 dependent on claim 4, characterised in that said magnetic barriers (50) are also provided for the second magnetic pallet-stone, each of these magnetic barriers being arranged so as to exert a magnetic force torque on the escapement wheel, having an opposite direction to that of said force torque supplied to this escapement wheel, when the escapement wheel is in an angular equilibrium position of the forces exerted thereon while the second magnetic pallet-stone is located at the magnetic potential energy gradient preceding this magnetic barrier; and in that the escapement is arranged such that, following said at least one shock on said second mechanical banking and before a subsequent tipping of the pallet assembly, the escapement wheel is immobilised in an angular stopping position.
11. Horological movement according to claim 9 or 10, characterised in that the periodic magnetised structure (36, 36A) is arranged such that the outer rim thereof is substantially circular, parts in the form of an arc of a circle of this magnetised structure, which respectively define said magnetic potential energy gradients, being arranged circularly around a axis of rotation of the escapement wheel.
12. Horological movement according to any one of claims 9 to 11, characterised in that said protruding parts (42) are formed by teeth which extend in a general plane wherein the first and second mechanical bankings (28, 29) which are formed respectively by two magnetic pallet-stones of the pallet assembly respectively supporting said magnet (30) and another magnet (32), forming the second magnetic pallet-stone, which are also located in the general plane, also extend.

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