EP3185083B1 - Mechanical timepiece mechanism with anchor escapement - Google Patents

Description

Field of the invention

The present invention relates to a mechanical watch movement comprising a balance and an escapement with an anchor associated with this balance. In particular the invention relates to a Swiss lever escapement.

Background of the invention

Mechanical watch movements equipped with a balance spring and a Swiss lever escapement have been known for a long time. This escapement comprises an anchor provided with a fork and a dart, a peg secured to the balance and cooperating with the fork to provide the pendulum maintenance pulses of its oscillation. Then, the watch movement further comprises two pins or starlets to limit the rotation of the anchor in both directions. These pins define for the anchor two rest positions between which it oscillates.

During each alternation of its oscillation, the anchor goes through various phases: a rest phase, a release phase, an impulse phase and a security phase. During the rest phase or period, the anchor is resting against a limiting pin, the escape wheel is stationary and the ankle traverses an additional arch upward and downward. The disengagement phase concerns the release of a tooth of the escape wheel bearing against a resting surface of a first pallet of the anchor during each rest phase. This phase is generated by the peg of the rocker which comes to bear against a first horn of the fork, the rocker then driving the anchor over an angular distance clearance. During the impulse phase, the second horn of the fork bears against the ankle and exerts a force on the latter through the torque of force provided by the escape wheel whose aforementioned tooth applies a force on a pulse surface of the first pallet. During this pulse phase, the balance receives a pulse to maintain its oscillation and the anchor continues its rotational movement over an angular pulse distance. Finally, during the safety phase, the ankle is released from the fork and it runs again an additional arch up and down. The anchor then carries out the terminal phase of its rotation over a safe angular distance, called 'lost path', which ensures the exit of the ankle from the fork and the positioning of an anchor wheel tooth against the surface. rest of the second pallet of the anchor.

During the rest phase, the anchor stinger ensures that the anchor remains substantially in its angular position of rest. In a main embodiment, there is provided a small plate integral with the balance shaft and having a cell to allow the rotation of the anchor during coupling between the ankle and the fork. The end of the stinger is located at a short distance from the lateral surface of the small plate when the anchor is in one of its two resting positions resting against a limiting pin. In particular during the rest phases, when a parasitic force acts on the anchor, the anchor can leave its bearing position against the pin and the sting then comes into contact with the lateral surface of the small plate; which will have the effect of disturbing the swinging movement of the balance. This results in a problem for the smooth running of the regulator. In any case it is desirable that such an event be as brief as possible. In a mechanical movement where the source of mechanical energy is supplied to the anchor wheel to maintain the oscillation movement, as is the case with a Swiss lever escapement described above, a draw is generated in the phases or periods of rest by the escape wheel cooperating with the pallet against which it is supported. This mechanical draw defines a restoring force for the anchor which causes it to be pressed alternately against the limiting pins and brings it back against these after shocks or strong accelerations suffered by the watch movement having momentarily lead the anchor in rotation.

We also know watch movements whose energy is supplied directly to the pendulum by a driving source, the pendulum then being a mechanical motor element which on the one hand transmits the energy to drive a gear and on the other hand is used to regulating the movement of the movement by means of counting its oscillation. In this context, the patent document CH 573136 describes an electrically maintained balance wheel and a system for counting its oscillations formed by an inverted anchor escapement. Electromechanical movements of this type have a very different arrangement and operation of watch movements equipped with a Swiss lever escapement. In particular, since the escape wheel is not subjected to any other source of energy than that coming from the balance wheel, this escapement wheel does not pull as in the case of a mechanical movement in which the driving energy is provided by a cylinder which drives in particular the escape wheel. As there is no mechanical draft, this document indicates that a print can be obtained by a magnet mounted on the anchor and two positioning pins a priori made of a ferromagnetic material. These pins continually attract the anchor, the overall force of attraction being directed towards the pin closest to the magnet, which allows to maintain the anchor in its rest positions during which they are alternately in support against these pins .

The Swiss lever escapement has been proven to ensure good regulation of a mechanical watch movement. However, such an escapement remains a complex mechanism and it has a sensitivity to shocks and strong accelerations as previously discussed. In particular, it is difficult to simultaneously optimize two parameters important that are the performance of such an exhaust and safety in case of shock, since the anchor is the first element concerned by these two technical characteristics. We know that even a small vibration or bouncing of the anchor during periods of rest cause a disruption of the pendulum (via the dart which comes into contact with the small plate and rub against it), which affects performance and to chronometry. In known embodiments, the drawing of the anchor and thus its holding against a limit stop of its rotation are provided solely by a certain torque applied to the anchor by the escape wheel. It can be seen that this torque may be too low, or even completely absent during part of the additional arc of the pin / balance, in particular in optimized escapements with a substantially constant torque because the escape wheel in such mechanisms advances slowly. .

Summary of the invention

The object of the invention is to solve the drawbacks of a traditional anchor escapement mentioned above and in particular to increase the restoring force against the limit stops during the rest periods of the anchor while limiting as much as possible. the consequences for the exhaust performance and the chronometry, even without harming them and even allow some improvement in the dynamic operation of the exhaust.

For this purpose, the invention relates to a mechanical watch movement in which the anchor of its exhaust carries at least one first permanent magnet which has a magnetization axis oriented substantially tangentially to its circular axis of displacement when the anchor undergoes movements. of rotation, this clock movement comprising a first element and a second element with high magnetic permeability respectively arranged on both sides of the at least one first permanent magnet so as to be substantially aligned on its circular axis of displacement. Then, the watch movement is remarkable in that it further comprises a second permanent magnet and a third permanent magnet respectively secured to the first and second elements with high magnetic permeability and each arranged on a side opposite to the at least one first magnet relative to these two elements with high magnetic permeability, and in that this at least a first magnet and a first assembly formed of the second magnet and the first element with high magnetic permeability, respectively a second assembly formed of the third magnet and the second element. with high magnetic permeability are arranged so as to generate, between the at least one first magnet and this first set, respectively this second set, a magnetic attraction force on a first section of the aforementioned angular distance and a magnetic repulsion force on a second section of this distance gular, and so that the second section corresponds to distances between them which are greater than the distances corresponding to the first section.

In a preferred embodiment, the first and second elements with high magnetic permeability have respective central axes which are substantially coincident with the respective magnetization axes of the second and third magnets, these respective central axes being substantially tangent to the circular axis. moving the first magnet.

Thanks to the characteristics of the invention, as will be explained in more detail later, a particular magnetic print is obtained which has the advantage of being exerted on only a relatively short angular distance from the rest position of the anchor in abutment against an element for limiting its rotation. This short angular distance is followed by an angular range in which the anchor is magnetically repelled from the aforementioned limiting element. Thus, in a Swiss lever escapement, the magnetic system of the invention, in addition to increasing the draw and consequently to limit the risks of disturbances of the oscillating movement of the balance, positively participates in the transmission of a maintenance pulse to the balance by the anchor to a central angular position of this anchor. Other advantages of the invention will also emerge from the detailed description of the invention.

Brief description of the drawings

• La Figure 1 est une vue en perspective d'un premier mode de réalisation d'un mouvement horloger selon l'invention;
• La Figure 2 est une vue partielle de dessus du mouvement horloger de la Figure 1 ;
• La Figure 3 montre schématiquement un dispositif magnétique formant une partie du système magnétique incorporé dans l'échappement du premier mode de réalisation;
• La Figure 4 est un graphe donnant la force magnétique subie par l'aimant mobile, dans le dispositif magnétique de la Figure 3, en fonction du déplacement de cet aimant mobile;
• La Figure 5 est un graphe montrant la force magnétique globale exercée sur l'ancre de l'échappement du premier mode de réalisation en fonction de sa position angulaire;
• Les Figures 6A et 6B montrent deux positions extrêmes possibles de l'ancre dans une période de repos de celle-ci pour un deuxième mode de réalisation de l'invention;
• La Figure 6C montre, sur le graphe de la Figure 5, la plage angulaire correspondante à l'ébat du dard dans le deuxième mode de réalisation;
• La Figure 7 est une vue latérale partielle du deuxième mode de réalisation depuis le plan VII -VII de la Figure 6A;
• Les Figures 8A, 8B et 8C montrent l'ancre du deuxième mode de réalisation dans respectivement trois positions de transition entre diverses phases d'une alternance de l'ancre;
• La Figure 9 montre, sur le graphe de la Figure 5, les trois positions de transition des Figures 8A, 8B et 8C ainsi que les diverses phases d'une alternance de l'ancre; et
• La Figure 10 est une vue latérale, similaire à celle de la Figure 7, d'une troisième mode de réalisation de l'invention.

Embodiments of the invention will be described hereinafter with the aid of the accompanying drawings, given by way of non-limiting examples, in which:

• The Figure 1 is a perspective view of a first embodiment of a watch movement according to the invention;
• The Figure 2 is a partial top view of the watch movement of the Figure 1 ;
• The Figure 3 shows schematically a magnetic device forming part of the magnetic system incorporated in the exhaust of the first embodiment;
• The Figure 4 is a graph giving the magnetic force experienced by the moving magnet, in the magnetic device of the Figure 3 as a function of the displacement of this movable magnet;
• The Figure 5 is a graph showing the overall magnetic force exerted on the escapement anchor of the first embodiment as a function of its angular position;
• The Figures 6A and 6B show two possible extreme positions of the anchor in a rest period thereof for a second embodiment of the invention;
• The Figure 6C shows, on the graph of the Figure 5 , the angular range corresponding to the frog of the stinger in the second embodiment;
• The Figure 7 is a partial side view of the second embodiment from the plane VII-VII of the Figure 6A ;
• The Figures 8A, 8B and 8C show the anchor of the second embodiment in respectively three transition positions between various phases of an alternation of the anchor;
• The Figure 9 shows, on the graph of the Figure 5 , the three transition positions of Figures 8A, 8B and 8C as well as the various phases of an alternation of the anchor; and
• The Figure 10 is a side view, similar to that of the Figure 7 of a third embodiment of the invention.

Detailed description of the invention

Referring to Figures 1 to 5 , hereinafter will be described a first embodiment of a mechanical watch movement 2 according to the invention. This watch movement comprises a conventional balance sprocket (not shown for the sake of clarity of the drawing) and an escapement of the Swiss anchor type (the escape wheel is not shown). The anchor 4 is provided at the end of its rod 10 with a fork 8 and a dart 12. It comprises a pivot shaft 18, mounted at one end in a bearing of a plate 6, and conventionally two arm 14 and 15 carrying pallets 16 and 17 respectively. The anchor can undergo rotational movements over an angular displacement distance between two extreme angular positions which respectively define two rest positions of this anchor. For this purpose, the watch movement comprises two limiting elements 24 and 25 of the rotation of the anchor which are respectively formed by two stars. In known manner, in operation, the anchor alternately abuts against the two limiting elements in periods of rest intervening between the pulses supplied to the balance by means of this anchor.

Anchor 4 carries two permanent magnets 20 and 22 which each have a magnetization axis substantially oriented tangentially to its circular axis of displacement 30 when the anchor is subjected to movement. rotation during its oscillation. The circular axes of displacement of the two magnets are merged. Then, the watch movement comprises two elements with high magnetic permeability 26 and 27 which are respectively arranged on both sides of the assembly formed by the two magnets 20 and 22, so as to be substantially aligned on the circular axis 30. In the variant represented at Figures 1 and 2 , the two magnets 20 and 22 are arranged on the fork 8 and the two elements 26 and 27 are respectively mounted on the two limiting elements 24 and 25. It will be noted that the two elements with high magnetic permeability and the two limiting elements present substantially the same plane of symmetry. The two magnets 20 and 22 are respectively arranged opposite the two elements 26 and 27 along the circular axis 30.

The watch movement further comprises two other permanent magnets 28 and 29 which are respectively integral with the two elements with high magnetic permeability. The magnet 28, respectively the magnet 29 is arranged on a side opposite the magnet 20, respectively the magnet 22 carried by the anchor relative to the element 26, respectively the element 27. Then, in projection along the circular axis of displacement 30, the magnet 20 has a polarity opposite to the polarity of the magnet 28 and the magnet 22 has a polarity opposite to the polarity of the magnet 29. two elements 26 and 27 have respective central axes which are substantially coincident with the respective magnetization axes of the magnets 28 and 29, these respective central axes being substantially tangent to the circular axis of movement of the magnets 20 and 22. The magnetic system formed of the various magnetic elements mentioned above thus comprises two identical magnetic devices arranged in an inverted manner on either side of a vertical plane of symmetry of the fixed magnetic elements. To expose the operation of each of these two magnetic devices incorporated in the escapement according to the invention, it is shown in FIG. Figure 3 a magnetic device 32 which is similar to the two devices provided in the first embodiment.

The device 32 comprises, on the one hand, a fixed assembly formed of a first magnet 28, respectively 29 and of a high magnetic permeability element 26, respectively 27 and, secondly, a second magnet 20, respectively 22 which is arranged mobile relative to the fixed assembly. Note that what will be explained below is also valid for the other embodiments of the invention. The element with high magnetic permeability is arranged between the first magnet and the second magnet. This intermediate element is arranged in contact with or near the first magnet. It consists for example of a carbon steel, tungsten carbide, nickel, FeSi or FeNi, or other alloys with cobalt such as Vacozet® (CoFeNi) or Vacoflux® (CoFe). The element with high magnetic permeability is characterized by a saturation field B _S and a permeability μ. The first and second magnets are for example ferrite, FeCo or PtCo, rare earths such as NdFeB or SmCo. These magnets are characterized by their remanent field.

The element with high magnetic permeability 26,27 has a central axis 34 which is substantially coincident with the magnetization axis of the first magnet and also with the magnetization axis of the second magnet. The respective magnetization directions of the magnets are opposite; that is to say that these magnets have inverted polarities along the central axis 34. This central axis corresponds to the axis of displacement of the second movable magnet.

Due to the arrangement of the high magnetic permeability element between the two magnets where this element is located and kept close to or against the first magnet, the movable magnet 20,22 is subjected to a global magnetic repulsion force. which tends to move away from the element 26,27 when the distance between the movable magnet and this element is greater than a distance D _inv ; while this movable magnet is subjected to a global force of magnetic attraction which tends to approach the element 26,27 and, if nothing opposes it, to maintain it against this element when the distance between the mobile magnet and this element is less than the distance D _inv . The overall force of magnetic attraction therefore defines a restoring force or pulling force of the moving magnet towards the element with high magnetic permeability despite the fact that the two magnets are arranged with their reversed polarities. Preferably, the distance between the first fixed magnet and the high magnetic permeability element is less than or substantially equal to one tenth of the length of this first magnet along its axis of magnetization.

Curve 36 of the Figure 4 gives the overall magnetic force acting on the moving magnet. This moving magnet undergoes, on a first section 38 of the relative distance D between it and the element 26,27, a generally magnetic attraction force which pulls it towards this element or presses against this element when it is in abutment. Then, the moving magnet undergoes, on a second section 40 of the relative distance D, globally a magnetic repulsion force. This second section 40 corresponds to distances, and therefore to relative distances D, between the high magnetic permeability element and the moving magnet which are greater than the distances corresponding to the first section 38. The distance D _inv is therefore a distance d inversion of the overall magnetic force that applies to the moving magnet. It depends in particular on the materials used and the geometry of each of the magnetic elements of the magnetic device 32, just as the intensity of the magnetic forces mentioned above. The maximum distance D _max between the element 26, 27 and the moving magnet 20, 22 is generally defined by the clock mechanism concerned. In the case of the escapement of the invention, this maximum distance is determined by a limiting element 24 or 25, just as the minimum distance between these elements. On the graph of the Figure 4 , the minimum distance is zero, but it is possible to arrange the moving magnet, the element 26,27 and the limiting element concerned so that this minimum distance is not zero. It is thus possible to adjust the maximum magnetic attraction force.

In the magnetic device 32, the axes of the magnets and the central axis of the element with high magnetic permeability are merged and are collinear with the axis of displacement of the moving magnet. However, it will be noted that this magnetic device can remain functional without these conditions, the direction of the relative movement being in particular able to present a certain angle with respect to the central axis 34. The axis of displacement of the movable magnet can be a circular axis when this magnet undergoes a rotational movement, as is the case in the exhaust according to the invention. In this case, it should be noted that it is preferable for the magnetization axes of the two magnets to tend to align when the distance between them decreases, in particular in the first section 38 of the relative distance D.

The remarkable operation of the magnetic device 32 is exploited in the escapement of the watch movement according to the invention which combines two such identical magnetic devices to generate an antisymmetrical magnetic behavior on the angular course of the anchor between its two positions of rest and define a bistable magnetic system for the anchor in the presence of a mechanical force exerted on it during the pulses supplied to the balance in both directions of its oscillation. More particularly, the first magnet 20 and a first assembly formed of the magnet 28 and the first element with high magnetic permeability 26, respectively the second magnet 22 and a second assembly formed of the magnet 29 and the second element with high permeability 27, are arranged to generate between the first magnet and the first set, respectively the second magnet and the second set a magnetic attraction force on a first section of an angular distance between them and a magnetic force of repulsion on a second section of this angular distance, and so that the second section corresponds to distances between them which are greater than the distances corresponding to the first section.

On the graph of the Figure 5 , the abscissa is represented as the circular distance between the fork 8 and the starlets 24 and 25 and in ordinate the overall magnetic force exerted on the magnets 20 and 22 carried by the anchor 4 in the magnetic system of the exhaust which is formed of two magnetic devices similar to the magnetic device 32. A curve 42 is obtained for this global magnetic force which has four distinct sections: a first section 46A where the overall magnetic force is a magnetic pulling force towards a first high magnetic permeability element 26, a second section 48A where the overall magnetic force is a magnetic repulsion force relative to the first element 26, a third section 48B where the overall magnetic force is a magnetic repulsion force relative to the second element with high permeability magnetic 27, and a fourth section 46B where the overall magnetic force is n new magnetic pulling force but this time towards the second element 27.

The curve 42 is substantially antisymmetric, the overall magnetic force being canceled at the central point 44. It will be understood that the behavior of the magnetic system is symmetrical starting from this central point, either towards the first limiting element 24, or towards the second limiting element 25 or, in other words, that the behavior of the magnetic system is the same that the anchor starts from a first limiting element in the direction of the second limiting element or vice versa. Thus, the magnetic forces are identical in both directions of rotation of the anchor and therefore in each of its alternations. The first and second sets mentioned above and the respective moving magnets carried by the anchor are arranged in such a way that a global magnetic force exerted by these first and second sets on the two mobile magnets and thus on the anchor substantially cancels out when the geometric center of these two magnets is located substantially in the plane of symmetry of the first and second sets (at the central point 44). Then, starting from this plane of symmetry along the circular axis of displacement of the moving magnets in the direction of the first set, respectively the second set, the global magnetic force defines in a first angular range (section 48A, respectively 48B) a magnetic repulsion force then, in a second angular range ( section 46A, 46B respectively) approaching the first set, respectively the second set, a magnetic attraction force relative to the first or second set. The magnetic system according to the invention thus generates, in a first part of a first half-alternation of any alternation of the anchor, a global force of magnetic attraction, defining a magnetic pull complementary to the mechanical draft generated by the escape wheel, and in a second part this first half-alternation a global force of magnetic repulsion.

We will describe below, using the Figures 6A to 9 a second embodiment of the watch movement according to the invention, in particular of its escapement 52, and additional explanations will be given as to the operation of this escapement in relation to the overall magnetic force which applies to the anchor in the magnetic system described above. This second embodiment has a magnetic system incorporated in the exhaust which operates in a manner similar to that involved in the first embodiment. The escapement 52 differs essentially from the escapement described above in that it comprises one and the same mobile magnet 54 carried by the anchor 4A. This movable magnet has a magnetization axis substantially oriented tangentially to its circular axis of displacement 30 when the anchor undergoes rotational movements. This moving magnet has a polarity of opposite direction to the respective polarities of the two fixed magnets 28 and 29 in projection along its circular axis of displacement. The only magnet 54 carried by the anchor replaces the two moving magnets of the first embodiment, so that it interacts with the two fixed magnetic assemblies and forms with each of them a magnetic device similar to the magnetic device 32 described above.

The escapement 52 is further distinguished by its two high magnetic permeability elements 26A and 27A which have a cylindrical shape. Next, it is distinguished by the positioning of the movable magnet 54 on the rod 10 of the anchor, the first and second fixed magnetic assemblies being arranged on either side of this movable magnet along its axis of displacement. Finally, in the escapement 52, the high magnetic permeability elements 26A, 27A also form the elements for limiting the oscillation movement of the anchor, the magnet 54 being held in abutment against these elements in the rest periods. from the anchor. Thus, the two elements with high magnetic permeability are respectively merged with the two limiting elements. To protect the movable magnet during shocks occurring at the end of alternations of the anchor, there is provided a protective layer 56 on both side surfaces of the oscillating magnet which abut respectively against the magnetic elements 26A and 27A.

The anchor 4A is provided with a stinger 12 cooperating with a lateral surface of the pivot shaft or a plate 58 mounted around the latter, this stinger serving to prevent the anchor from moving away from more than an angular safety distance when the anchor is in any of its two rest positions during its rest periods. The balance is shown in cross-section above the small plate 58. This rocker comprises a peg 60 secured to its pivot shaft and which cooperates with the fork 8A to allow the latter to provide the pendulum pulse maintenance of its oscillation by a driving force applied to an escape wheel (not shown) which is coupled to the anchor. It will be noted that the fork 8A extends the rod 10, the pin 12 being arranged below the general plane of the anchor.

The Figure 6A shows the anchor 4A in a rest position, the movable magnet being in abutment against the magnetic element 26A. Note that, in this configuration, the anchor - stop distance (limiting element) is defined as zero. In the variant described here, in the zero position, the magnet 54 is however at a distance from the magnetic element 26A corresponding to the thickness of the protective layer 56. In this normal resting configuration occurring during the rest phases of the anchor, this anchor is in abutment against a limiting element and it first undergoes a mechanical pulling force via a torque applied to the anchor by the escape wheel and secondly, according to the invention, a pulling force magnetic in the direction of said limiting element.

In a preferred variant, the magnetic system of the invention is arranged in such a way that, in periods or phases of rest, the angular pitch distance of stinger 12 is less than or substantially equal to the angular distance of magnetic pull corresponding to the stub 46A, respectively 46B on the graph of the Figure 5 . In these two sections 46A and 46B, the overall magnetic force is a force of magnetic attraction towards the limiting element located, in projection in the general plane of the anchor, the closest to the longitudinal axis of the rod 10 of the anchor. The Figure 6B shows a configuration where, during an impact, the dart momentarily bears against the lateral surface of the plate 60 and the Figure 6C shows that the angular distance of the sting is here substantially equal to the angular range of magnetic attraction (magnetic pull). This ensures a good functionality of the magnetic print, avoiding that the magnetic system generates in case of shocks a magnetic force that would oppose the mechanical draft; which could then increase the effect of disturbances and in particular the friction of the sting against the small plateau.

The escapement of the second embodiment is shown in FIGS. Figures 8A, 8B and 8C in three successive positions corresponding to transition zones between various phases of an alternation of the anchor which have been previously exposed in the background of the invention. These three successive positions are indicated in Figure 9 on the curve 42 of the overall magnetic force by the three points 42A, 42B and 42C. During the rest phase, the anchor is normally in the zero position bearing against a first limiting element, as shown in FIG. Figure 6A . The angular range between the zero position and the first position 42A defines most of the clearance phase for the anchor. It is expected that the release of the anchor extends, for safety reasons during the rest phase, an angular distance greater than that of the stinging of the sting. During the first part of the disengagement phase, the anchor undergoes a mechanical draw, generated by the escape wheel, and a magnetic pull. Thus, the magnetic draft and mechanical draft are complementary and can be sized to optimize the total draw. During the release, the beam causes the anchor by the contact between his ankle (also called ellipse seen its shape) and a first horn of the fork. It should be noted that the magnetic attraction force does not necessarily require a surplus of energy dissipation of the balance to release the anchor, because the pull gain generated by the magnetic pull reduces mechanical draft and optimize thus the contact between the teeth of the escape wheel and the pallets of the anchor. In addition, advantageously, this optimization makes it possible to promote the mechanical pulse of the anchor in the pulse phase.

After the clearance itself, the anchor advances under the impetus of the escape wheel until the second horn of the fork collides with the ankle (this period of catching of the pendulum is in this presentation located in the clearance phase, but it can also be considered as a separate phase). Initially the magnetic attraction force opposes the movement of the anchor but this force decreases rapidly with the angular distance. The disengagement phase can take place over an angular distance corresponding to 10% -20% of the total travel of the anchor between the two elements of limitation of its rotation. It will be noted that during the catch-up period, the magnetic force is very small and negligible in the example corresponding to curve 42.

Then, substantially until the angular position 42C occurs the impulse phase where the anchor provides energy to the balance (maintenance). The corresponding angular pulse distance is represented at Figure 9 . What is remarkable is that during the first part of the angular impulse distance which constitutes the major part of this angular distance of impulse, the global force of magnetic repulsion favors the acceleration of the anchor. In other words, the maintenance pulses are each supplied to the pendulum substantially over an angular pulse distance and the magnetic system of the invention is arranged so that most of this angular pulse distance is located in the angular range of magnetic repulsion 48A relative to the limiting element of which the movable magnet 54 moves away in the alternation considered here, that is to say before the central point 44 on the graph of figures 5 and 9 .

It will be noted that at the end of the impulse phase there is a slight magnetic braking (in the magnetic repulsion range 48B which for the alternation considered here defines a magnetic braking range for the rotating anchor). This terminal magnetic braking dissipates very little energy during the pulse phase. It will be noted that it then continues during the security phase; which is an advantage for limiting the shock against the second limiting element. During this safety phase, the anchor travels, after receiving a maintenance pulse, a safety angular distance before reaching the second limiting element. Preferably, the magnetic system of the invention is arranged in such a way that the angular safety distance is for the most part situated in an angular range of magnetic braking of the anchor in rotation and therefore magnetic repulsion relative to the second limiting element of which the movable magnet 54 approaches. Finally, in the terminal part of the safety phase, the anchor is accelerated under the effect of a global magnetic attraction force towards the second limiting element, which again constitutes a magnetic pulling force for the period of time. next rest of the anchor.

To the Figure 10 is shown a third embodiment in side view in a sectional plane through the rod 10 of the anchor 4A. The watch movement 60 is distinguished from the previous one essentially by the shape of the elements with high magnetic permeability 26B and 27B and more generally by the configuration of the two fixed magnetic assemblies 62 and 64. The watch movement comprises a base 6 (platinum or bridge) on which are arranged these two sets. Each magnetic assembly comprises a support 66, respectively 67 in which are arranged a spherical ferromagnetic element 26B, respectively 27B and a cylindrical magnet 28A, respectively 29A. The support is secured to the base, which is indicated schematically by a screw assembly of the support to this base. Other fastening means may be provided. Each support has a parallelepipedal external shape and has a central opening of cylindrical or parallelepipedic overall shape. In the case where the opening is parallelepipedic, the magnet may also have such a shape as in the examples of the previous embodiments. At a first end of this central opening, on the side of the spherical ferromagnetic element, is provided a transverse projection 70 forming a stop for the spherical ferromagnetic element, thus preventing it from fully emerging from the opening while allowing that a part of this element comes out of the support and thus the movable magnet 54 can come into contact with this spherical element. As a result of the spherical ferromagnetic element is arranged in the opening of the corresponding support the magnet 28A, respectively 29A, which is in contact with the spherical ferromagnetic element. On the side of the magnet, the opening is closed by an end wall 68 welded or glued to the body of the support.

It will be noted that the spherical shape for the two elements with high magnetic permeability is interesting because it is possible to achieve ferromagnetic microbeads with a very high precision and a very good surface state, without affecting the magnetic properties of these elements. In addition, for tribology and during shocks with the oscillating magnet 54, it is preferable to have the anchor press against a ball rather than against a flat surface that may be irregular and not perfectly parallel to the hard layer. deposited on the side surfaces of the magnet.

Claims (10)

1. Mechanical timepiece movement comprising a balance provided with a pivot shaft and an escapement associated with said balance, said escapement comprising a pallet-lever (4; 4A) provided with a fork (8; 8A), an impulse pin (60) integral with the balance and cooperating with the fork to allow the latter to provide the balance with impulses maintaining the oscillation thereof by means of a drive force applied to an escape wheel, which is coupled to the pallet-lever, said timepiece movement further comprising two banking elements (24, 25; 26A 27A) preventing rotation of the pallet-lever, which define the two locking positions thereof and between said positions an angular distance for the pallet-lever, said pallet-lever being arranged to move alternately into abutment with the two banking elements in locking periods occurring between said impulses provided to the balance; characterized in that the pallet-lever carries at least a first permanent magnet (20, 22; 54) which has an axis of magnetisation oriented substantially tangentially to the circular axis of displacement (30) thereof, when the pallet-lever is subjected to said movements of rotation; in that the timepiece movement comprises a first element (26; 26A) and a second element (27; 27A) of high magnetic permeability respectively arranged on either side of said at least a first magnet so as to be substantially aligned on the circular axis of displacement (30) thereof, the first and second elements of high magnetic permeability and the two banking elements having substantially the same plane of symmetry; in that the timepiece movement further includes a second permanent magnet (28; 28A) and a third permanent magnet (29; 29A) respectively integral with the first and second elements of high magnetic permeability and each arranged on an opposite side to said at least a first magnet relative to said respective two elements of high magnetic permeability; and in that said at least a first magnet and a first assembly formed of the second magnet and the first element of high magnetic permeability, respectively a second assembly formed of the third magnet and the second element of high magnetic permeability, are arranged to generate, between said at least a first magnet and said first assembly, respectively said second assembly, a force of magnetic attraction on a first section (38) of said angular distance and a force of magnetic repulsion on a second section (40) of said angular distance, and such that the second section corresponds to distances of separation between them which are greater than the distances of separation correspond to the first section.
2. Timepiece movement according to claim 1, characterized in that the first and second elements of high magnetic permeability have respective central axes that are substantially coincident with the respective axes of magnetisation of the second and third magnets, said respective central axes being substantially tangent to the circular axis of displacement (30).
3. Timepiece movement according to claim 1 or 2, characterized in that said at least a first magnet consists only of said first magnet (54) which has an opposite polarity to the respective polarities of the second and third magnets in projection along said circular axis of displacement.
4. Timepiece movement according to claim 1 or 2, characterized in that said at least a first magnet is formed by said first magnet (20) and a fourth magnet (22), said fourth magnet also having an axis of magnetisation substantially oriented tangentially to said circular axis of displacement, said first and fourth magnets being respectively arranged facing the first and second elements of high magnetic permeability along said circular axis of displacement; and in that, in projection along said circular axis of displacement, the first magnet has an opposite polarity to the polarity of the second magnet (28), and the fourth magnet has an opposite polarity to the polarity of the third magnet (29).
5. Timepiece movement according to any of the preceding claims, characterized in that the first and second elements of high magnetic permeability (26, 27) are respectively mounted on the two banking elements (24, 25).
6. Timepiece movement according to any of claims 1 to 4, characterized in that the two elements of high magnetic permeability also form the two banking elements so that the two elements of high magnetic permeability are respectively coincident with the two banking elements, and in that said two elements are of spherical shape.
7. Timepiece movement according to any of the preceding claims, characterized in that said first and second assemblies and said at least a first magnet are arranged such that an overall force of magnetic attraction, exerted by the first and second assemblies on said at least a first magnet, is substantially cancelled out when the centre of said at least a first magnet is substantially in said plane of symmetry (44), and starting from said plane of symmetry along said circular axis of displacement in the direction of said first assembly, respectively said second assembly, defines, in a first angular range (48A, 48B), a force of magnetic repulsion and then, in a second angular range (46A, 46B) moving closer to the first assembly, respectively the second assembly, a force of magnetic attraction relative to said first or second assembly.
8. Timepiece movement according to claim 7 and wherein the pallet-lever is provided with a guard pin (12) cooperating with a lateral surface of said pivot shaft or of a roller (58) mounted around the latter, said guard pin being used to prevent the pallet-lever drawing away further than an angular distance of clearance (43A) of the guard pin when said pallet-lever is in either of its two locking positions during said locking periods, characterized in that said second angular range is substantially equal to or greater than said angular distance of clearance of the guard pin.
9. Timepiece movement according to claim 7 or 8 and wherein said maintaining impulses are each provided to the balance substantially over an impulse angle (43C), characterized in that said first and second assemblies and said at least a first magnet are arranged such that most of this impulse angle is located within said first angular range (48A; 48B) relative to the banking element which said at least a first magnet moves away from during any vibration of the pallet-lever.
10. Timepiece movement according to any of claims 7 to 9 and wherein the pallet-lever travels, after having received any of said maintaining impulses, through a safety angular distance (43D) before reaching abutment with one or other of the two banking elements, characterized in that said first and second assemblies and said at least a first magnet are arranged such that the safety angle is mostly situated in said first angular range (48A; 48B) relative to the banking element which said at least a first magnet moves closer to during any vibration of the pallet-lever.

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