Watch with mechanical movement with force control mechanism

Abstract

The watch (1) has a mechanical movement with a force-control mechanism and is of the jumping seconds type. The force-control mechanism is located in a finishing gear of the mechanical movement between a power source and an escapement wheel (11) linked to an oscillator (14) which rotates to drive the escapement wheel in the same direction of rotation. The escapement wheel meshes with a seconds wheel (2). A rotating locking element (7) is arranged to cooperate with a stop mechanism (3) connected to the fixed seconds wheel (SFA) to lock the finishing gear in a stopped position or release it in a jumping position depending on the angular position of the seconds wheel. A flexible guide (4) with elastic blades (4a) is fixed on one side to the seconds wheel and on the other side to the movement support.The pre-cocked flexible guide is designed to rotate the fixed seconds wheel (SFA) and the oscillator-linked escapement mechanism with each half-oscillation of the oscillator in stop mode. In jump mode, the finishing gear is released, allowing the rotary locking element to rotate and drive a seconds pinion (5) coaxial with the fixed seconds wheel to perform a one-second jump. This also allows the flexible guide to be re-cocked in conjunction with the seconds pinion, while simultaneously locking the rotary locking element and the finishing gear for the stop mode following the jump mode.

Description

Field of invention

[0001] The invention relates to a watch with a mechanical movement having a force control mechanism, such as the force due to gravity when wearing the watch and of the jumping second type. Preferably, the force control mechanism may be a tourbillon mechanism mounted at the escapement. The tourbillon cage surrounds the escapement mechanism and preferably the cage completes a rotation every minute with in particular 60 jump seconds performed. Background of the invention

[0002] As a reminder in watchmaking, a tourbillon, also called a "rotating cage", is a watchmaking complication, added to the escapement mechanism, intended to improve the precision of mechanical watches by counterbalancing the disturbances of the isochronism of the resonator due to the Earth's gravity. The fundamental criterion, which marks a tourbillon, in comparison with a carousel in particular, is the presence of a fixed gear train on which the tourbillon cage meshes. Generally, the tourbillon cage is rotatably mounted between two fixing points.

[0003] Gravity is also taken into account to compensate for any disturbances in the resonator's isochronism. The escapement is coupled to the resonator. It interacts with it once or twice per oscillation period. The angle traveled by the resonator during the interaction is called the lift angle. The remainder of the resonator's path is called the supplementary angle or arc.

[0004] During the additional angle, the resonator can be in contact with the escapement (friction rest escapement) or without contact (free escapement). During the lift angle, the escapement performs two main phases, which are the release (or counting) and the impulse (or sustaining).

[0005] In a watch complication, the jumping seconds aim to display the second in steps of a whole second, which corresponds on a 60-second dial to 6° of angle per second. This jumping seconds is often associated with constant force mechanisms which take advantage of the particular construction of this jumping seconds. Deadbeat or fixed seconds mechanisms also approach these constructions with the particularity of being able to stop the second at will like a chronograph.

[0006] Several jumping seconds mechanisms exist in watchmaking literature and patents, and are used. Some examples include the Blancpain 1195 movement in a Jacquet Droz watch. Breguet's Marie Antoinette uses a deadbeat seconds mechanism.

[0007] Patent application WO 2011 / 157797 A1 describes a mechanism for periodically jumping forward a pivoting cage carrying a wheel and an escape pinion and an anchor cooperating with the wheel and a balance spring. In addition, it comprises retaining means for allowing or preventing the pivoting of said cage depending on the movements or not. There are also stopping means for allowing or preventing the pivoting of the retaining means depending on their angular position. A constant force device periodically makes the retaining means cooperate. This device comprises a whip designed to make complete revolutions.

[0008] The principle of these mechanisms described is to retain the gear train between the escapement and the second hand by a mechanism, while an auxiliary spring maintains the escapement with a constant force in a stopping phase. At the end of the second, which is counted by the escapement, the released gear train allows the advancement of one second. Thus the display advances and the mechanism is rearmed in the jump phase.

[0009] In such a mechanism operating at frequencies close to a second, the torques available in watchmaking are very low. This is why these mechanisms are difficult to produce and generally unreliable.

[0010] In the mechanism of the Blancpain 1195 movement, there is a stop system that distributes part of the torque into the stop phase lock to compensate for friction. This results in a jumping second with an angular displacement of approximately 20% in the stop phase for an 80% jump.

[0011] It may also be considered to reduce the frequency and to use dead minutes instead of seconds, which makes construction easier.

[0012] Some of these mechanisms can become desynchronized after complete disarming, and go into a blocked position. This requires a stop system linked to a power reserve mechanism, which will stop the mechanism before complete disarming.

[0013] In a mechanism described in patent EP 1 528 443 B1, a constant force device is proposed for a watch, with deadbeat seconds. This device makes it possible to move an axis of a mobile on a lever controlled by an energy storage spring, which tends to pivot the lever. The device comprises a pinion of a first seconds wheel of the movement, which meshes with a setting wheel pivotally mounted on this lever, and which meshes with the pinion of a second seconds wheel defining the mobile. The lever carrying a finger must adapt to cooperate with a ratchet toothing of a stop wheel, which meshes with the first seconds wheel. When the finger is engaged with a radial flank of the ratchet, the gear train is blocked, in particular composed of the first seconds wheel and the setting wheel without transmission of force from the first seconds wheel and the setting wheel.The second wheel is controlled by the escapement and only turns when the latter is moved by the balance wheel. The spring is wound by moving the lever in the opposite direction, for which the spring exerts a lower torque on the lever than that exerted by the barrel spring on the lever, when the stop wheel is released. The device thus allows the adaptation of the winding / unwinding cycle according to the number of teeth of the stop wheel. This device allows a jumping seconds function to be ensured, but the main disadvantage is that it is not easy to realize with a large number of components required to carry out this operation. In addition, there is a movement of a mobile at the time of the jumping seconds, which is not desired.

[0014] Utility model CN ​​209014916 U describes a tourbillon clockwork mechanism having a toothed wheel. The toothed wheel is composed of a central portion for the passage of an axle, connected by spring-type metal coils to an inner wall of a crown with external peripheral teeth.

[0015] Patent EP 3 356 690 B1 describes a watch component having a flexible pivot of the well-known separate crossed blade type, and having means for adjusting the position of the crossing point of the blades.

[0016] Document WO 2018 / 193365 A1 describes in Figure 8 a timepiece with a force control mechanism comprising a jumping second wheel and a rotating locking device. Summary of the invention

[0017] For the present invention, it is sought to produce a jumping seconds display and still constant force in a simpler manner, without movement of the mobile and without risk of desynchronization at the end of winding and thus limiting friction for use in particular in a tourbillon movement.

[0018] The invention therefore aims to overcome the drawbacks of the state of the art by providing a watch with a mechanical movement with a force compensation or control mechanism of the jumping second type, overcoming the drawbacks of the aforementioned prior art devices.

[0019] To this end, the invention relates to a watch with a mechanical movement with a force compensation or control mechanism of the jumping second type, which comprises the characteristics defined in independent claim 1.

[0020] Particular embodiments of the watch with mechanical movement with compensation mechanism or force control of the jumping second type are also described in dependent claims 2 to 18.

[0021] An advantage of the mechanical movement watch with force control mechanism according to the invention lies in the fact that it comprises a seconds wheel to accumulate the energy necessary to maintain several oscillations of the escapement mechanism with the oscillator, in particular in a stop mode before switching to a jump mode. Depending on the frequency of the resonator equipped with a traditional escapement, the seconds wheel maintains a few oscillations of the resonator or oscillator without part of the gear train coming from the barrel being driven. Preferably, the seconds wheel releases a blocking element, such as a whip after a certain number of oscillations to move in particular the tourbillon cage by 6° in the clockwise direction (SAM) and the finishing gear train coming from the barrel defining a seconds wheel of the jumping seconds type.In the case of the tourbillon according to an exemplary embodiment at at least the fifth pulse of the 2.5 Hz oscillator, the whip is released and by it, the intermediate wheel linked to the whip, the medium wheel, the large medium wheel and the barrel to drive the tourbillon cage by a step of 6° in a direction opposite to the accumulation of the second wheel. Primarily, the tourbillon cage can be moved angularly after a certain number of oscillations defining a second. By this arrangement without moving the mobile, the risk of desynchronization at the end of winding is not affected.

[0022] Advantageously, the seconds wheel is intended to move in the stop phase by a certain number of small steps following the oscillations of the spiral spring of the oscillator linked to the escapement mechanism, which is of the Swiss anchor type. In this stop phase or stop mode, the seconds wheel rotates counterclockwise while being rotated by a flexible guide with elastic blades, which is pre-wound. A movable portion of this flexible guide is fixed on a face of the seconds wheel, while a fixed portion of this flexible guide is fixed on a support of the watch movement, such as a plate. The movable portion of this flexible guide is preferably fixed directly below the seconds wheel. The flexible guide is mounted by an axial opening, coaxially with a seconds pinion, which is the seconds and tourbillon pinion.

[0023] Advantageously, the flexible guide with elastic blades (spring blades) comprises several elastic blades in series connecting more massive parts including the mobile and fixed portions of the flexible guide, and possibly other intermediate portions. The flexible guide with elastic blades in series can thus be produced with a more robust structure capable of ensuring the rotation of the second wheel with a return torque advantageously used to replace the spring of the force control mechanism and with better axial support. In addition, such a flexible guide with elastic blades allows for an absence of friction, wear and energy dissipation, as well as an absence of play and precise guidance. Brief description of the drawings

[0024] The aims, advantages and characteristics of the watch with mechanical movement with compensation mechanism or force control will appear better in the following description, in particular with regard to the drawings in which: there figure 1 represents a three-dimensional view from below of the main elements of the watch movement with force control mechanism and of the jumping second type according to the invention, the figure 2 represents a bottom view of the mechanical watch movement with force control mechanism of the jumping second type without the middle wheel and the intermediate wheel according to the invention, the Figures 3a, 3b and 3c represent plan views of three embodiments of flexible guides with elastic blades or pivots with flexible blades with higher torques and better axial support to be able to be connected to the second wheel according to the invention, the figure 4represents a view from below of another schematic embodiment of a traditional mechanical watch movement with the finishing train without tourbillon and the force control mechanism according to the invention, and the Figure 5 represents a cross-section from bottom to top of the mechanism in the center of the tourbillon as shown above partially at the figure 1 . Detailed description of the invention

[0025] In the following description, various organs or elements of the mechanical watch movement with force control mechanism and of the jumping second type, which are well known in this technical field, will only be described briefly.

[0026] It should first be noted that the watch with a mechanical movement with a force control mechanism and of the jumping second type can be with a tourbillon whose cage encloses an oscillator and an escapement mechanism as explained below, or according to a traditional mechanical movement without a tourbillon, which will be explained later with reference to the figure 4 .

[0027] THE Figures 1 and 2 represent a part of a mechanical watch movement 1 which is shown without the energy source, such as the barrel which is the mainspring and which is connected, in this case, to a fusee connected by a chain to the barrel drum for its drive. Also not shown is a large medium wheel, which is driven in rotation by a toothing on the periphery of the fusee according to a traditional embodiment. This energy is applied in the form of a torque on the pinion of the medium wheel 10.

[0028] THE Figures 1 and 2therefore represent a part of a mechanical watch movement comprising a finishing train 5, 8, 9, 10 in which is arranged a force control mechanism of the mechanical watch movement 1. This force control mechanism may be similar to a constant force device. The finishing train is arranged between a source of energy not shown, which is preferably a spring barrel, and an escapement mechanism, for example with a Swiss lever 13 and having an escape wheel 11 in the form of a wheel, retained and released alternately by an oscillator 14, which is preferably a balance spring and the energy for maintaining its oscillation is provided by said escape wheel 11. The escape wheel 11 is arranged to be able to rotate in the same direction of rotation at each half-oscillation of the oscillator 14.

[0029] The escape wheel 11 meshes with a second wheel 2 which is hereinafter also defined as a fixed second wheel SFA. This second wheel 2 is called a fixed second wheel SFA, even if it is not fixed in its operation. This fixed second wheel SFA 2 can rotate counterclockwise (CCW) to maintain the operation of the escapement mechanism linked to the oscillator in a stop mode, and rotate clockwise (CW) in a jump mode to perform a jump corresponding to 1 second. Both in the execution form with a tourbillon, and in the execution form without a tourbillon, there is always a stop phase and a jump phase so as to make a jump on the display corresponding to one second.

[0030] To do this, the fixed seconds wheel SFA 2 preferably comprises peripheral teeth meshing with a toothed escape pinion 12 coaxial with said escape wheel 11. As explained below in a stopping phase of the finishing train, the fixed seconds wheel SFA 2 rotates counterclockwise (CCW) by the restoring force of the flexible guide 4 and drives the escape wheel 11 at each half-oscillation of the oscillator 14 via the toothed escape pinion 12 so as to maintain the operation of the oscillator and the escapement mechanism in this stopping phase.

[0031] During this stopping phase, the fixed seconds wheel SFA 2 pivots in SIAM on its flexible guide 4 around the tourbillon cage 15 without touching the latter, which is stopped. This SIAM pivoting of the SFA 2 is carried out until the moment of release of the finishing gear train 5, 8, 9, 10 by which a jump of one second is carried out by the tourbillon cage 15 and its second pinion 5, driving with it the fixed seconds wheel SFA 2, which is linked to the escapement wheel 11, in the clockwise jump phase SAM.

[0032] To define the stop phase and the jump phase, the force control mechanism comprises on the one hand a rotary locking element 7 arranged to cooperate with a stop member 3 in connection with the fixed second wheel SFA 2 in the stop mode. As illustrated in Figures 1 and 2, this stop member 3 may be a rack 3, rotatably mounted at a first end of the rack 3 around an axis 33 arranged for example between a movement mounting plate and a middle bridge not shown. A second free end of the rack 3 comprises in a locking part, a finger-shaped edge portion 3b freely arranged inside a guide housing between two teeth of a cam 6. The cam 6 is fixed integrally with said fixed second wheel SFA 2 near its center so as to rotate the rack 3 in each direction. The second free end of the rack 3 further comprises a stop piece 3a, such as a pallet 3a, arranged on a side opposite the edge portion 3b and arranged to block the rotary locking element 7 in a stopping mode. The pallet 3a can be made of a hard material reducing friction with the locking element 7 in contact with the pallet 3a in a stopping phase.This stop piece, which is the pallet 3a, can be made of a friction-reducing material such as ruby.

[0033] To rotate the fixed second wheel SFA 2, particularly in a stop mode, a flexible guide 4 with elastic blades 4a or spring blades, which is pre-wound, is connected directly to the fixed second wheel SFA 2. The flexible guide 4 acts as a spring on the fixed second wheel SFA 2. To do this, the flexible guide 4 comprises a movable portion 4c with at least one opening 17 but preferably two openings 17 for attachment to a face of the fixed second wheel SFA 2. Preferably, the flexible guide 4 is attached to a lower face of the fixed second wheel SFA 2.

[0034] It should be noted that elastic blades 4a are defined, these blades can be of rectangular, hexagonal or even round cross section. These elastic blades have a geometry: length and section which must be well determined to ensure the spring function to drive the fixed second wheel SFA 2 in rotation with the necessary torque. We can refer to the WH Wittrick work indicated below, for the production of flexible guides 4 with elastic blades 4a.

[0035] As shown in the Figure 5, at least one fixing means 27 in or through the opening(s) 17 is thus provided to fix the fixed second wheel SFA 2 on the movable portion 4c of the flexible guide 4. Preferably, this fixing means 27 may be at least one material extension of the fixed second wheel SFA 2 to form a single piece with the wheel. Two material extensions 27 may be provided to be inserted for example by force respectively into the two openings 17 of the movable portion 4c of the flexible guide 4 to ensure a good hold and without protruding from each opening 17. A border may also be provided around each material extension 27 and may come directly from the same material with the corresponding material extension to ensure a space between the lower face of the fixed second wheel SFA 2 and an upper face of the flexible guide 4.

[0036] The flexible guide 4 further comprises a fixed portion 4b with at least one opening 16, but preferably two openings 16 to be mounted and fixed by means of a screw and nut assembly not shown on a support of the watch movement, such as a plate. Several elastic blades 4a or portions of elastic blades connect the mobile portion 4c to the fixed portion 4b as well as intermediate portions possibly between the mobile 4c and fixed 4b portions. The flexible guide 4 is mounted by an axial opening, coaxially with the second pinion 5, and around an axial tube of the fixed second wheel SFA 2 coaxial with the axis of the second pinion 5.

[0037] It should also be noted that it may be envisaged to have two fixing openings provided in the fixed seconds wheel SFA 2 to receive by force insertion two extensions of material of the movable portion 4c of the flexible guide 4 in an equivalent manner but inversely to what has been described above. The fixing means may also be a screw and nut assembly passing through openings in the movable portion and the fixed seconds wheel SFA 2, but with this type of assembly, too much space is wasted. Similarly, the fixing of the fixed portion 4b of the flexible guide 4 on the plate may be carried out by a means other than the screw and nut assembly, taking the example of the fixing of the fixed seconds wheel SFA 2 on the flexible guide 4.In the rest position, that is to say upon transition from the jump mode to the stop mode, the elastic blades 4a of the flexible guide 4 must be prestressed to accumulate mechanical energy to rotate the fixed second wheel SFA 2 in particular in the counterclockwise direction (SIAM).

[0038] The rotation of the fixed seconds wheel SFA 2 also drives the escape wheel 11 via an escape pinion 12 coaxial with the escape wheel of the Swiss lever escapement mechanism 13. This is advantageous for keeping the escapement mechanism with the oscillator 14 in operation in this stopping phase by the mechanical energy stored in the flexible guide 4 with elastic blades 4a acting on the fixed seconds wheel SFA 2 to rotate it in a counterclockwise direction (SIAM).

[0039] The rack 3 is connected without the action of a spring to a cam 6 fixed on the fixed second wheel SFA 2 to block or release said finishing gear train according to the angular position of said fixed second wheel SFA 2 by retaining a whip 7, as a blocking element. This whip 7 comes into contact with a stop piece 3a of the blocking part of the rack 3. This stop piece is a pallet 3a, as described above.

[0040] In the case shown, the fixed seconds wheel SFA 2 can rotate by 5 small steps corresponding to 6° of angle representing 1 second in the opposite direction. The whip 7 is itself driven by the going train and retained by the stop piece 3a. Once released at the end of the stopping phase, the rotation of the rack 3 releases the whip 7 which triggers the jump phase. During the jump phase, the whip 7 performs a rotation corresponding to a jump of 1 second, driven by the going train, in the case shown, a half-turn. The going train similarly drives the tourbillon cage 15 via the second pinion 5 and the fixed seconds wheel SFA 2 in a clockwise direction (SAM), which resets the flexible guide 4.This flexible guide 4 of the fixed seconds wheel SFA 2 is arranged to accumulate energy when said fixed seconds wheel SFA 2 is driven in SAM during the jump phase and to restore it to said fixed seconds wheel SFA 2 in SIAM during the stop phase.

[0041] Generally in the stop phase, several half-oscillations of the oscillator 14 occur before the release of the going train. This means that the frequency of the oscillator 14 is generally higher than 1 Hz and for example in this case, can be set at 2.5 Hz. Since the fixed seconds wheel SFA 2 rotates in the stop phase with each small step corresponding to a half-oscillation (alternation), 5 half-oscillations of the oscillator 14 can be counted in the stop phase until the moment of the release of the rotating blocking element 7 for the jump phase. The flexible guide 4 linked to the fixed seconds wheel SFA 2 must therefore provide energy during the 5 half-oscillations of the oscillator 14 or the cage is stopped, and be re-wound during the jump of said cage 15.

[0042] The flexible guide 4 shown in the figure 2comprises a fixed portion 4b arranged in a wide V-shaped opening housing of the movable portion 4c, which comprises an axial opening, which is coaxial with the axis of the second pinion 5. Two through openings 16 are provided in the fixed portion 4b and arranged on the same line with the axial opening. Two through openings 17 are provided in the movable portion 4c and arranged practically on the same line with the axial opening.

[0043] In this embodiment, five successive elastic blades 4a connect a first inner side of the movable portion 4c to a first inner side of the fixed portion 4b. A first elastic blade 4a from the movable portion 4c is connected to a first intermediate central portion. A second elastic blade 4a from the first intermediate central portion is connected to a first intermediate peripheral portion. A third elastic blade 4a from the first intermediate peripheral portion is connected to a second intermediate central portion. A fourth elastic blade 4a from the second intermediate central portion is connected to a second intermediate peripheral portion. A fifth elastic blade from the second intermediate peripheral portion is connected to a first inner side of the fixed portion 4b.

[0044] Five successive elastic blades 4a connect a second inner side of the movable portion 4c to a second inner side of the fixed portion 4b. A second elastic blade 4a from the movable portion 4c is connected to the same first intermediate central portion. A second elastic blade 4a from the same first intermediate central portion is connected to the same first intermediate peripheral portion. A third elastic blade 4a from the first intermediate peripheral portion is connected to the same second intermediate central portion. A fourth elastic blade 4a from the second intermediate central portion is connected to the same second intermediate peripheral portion. A fifth elastic blade from the second intermediate peripheral portion is connected to a first inner side of the fixed portion 4b.

[0045] It can be seen that the fixed part 4b is arranged inside between the movable portion 4c and the two intermediate peripheral portions. In addition, the two intermediate central portions form an arc of a circle centered on the axis of the second pinion 5, and the same is true for the two intermediate peripheral portions also centered on the axis of the second pinion 5.

[0046] However, more or less half-oscillations of the oscillator 14 can be provided in the stop phase depending on the oscillation frequency of the oscillator 14. Each half-oscillation must be equal to 0.2 s for a 2.5 Hz oscillator. The number n of half-oscillations of the oscillator can therefore be chosen only for an oscillator frequency greater than 1 Hz, for example for at least n = 3 half-oscillations for 1.5 Hz or n = 5 for 2.5 Hz. The number of small steps made by the fixed seconds wheel SFA 2 in the stop phase must correspond to a jump of 1 second in the jump phase.

[0047] It is also possible to consider making jumps with a period greater than 1 second, which generalizes the above rule to an oscillator frequency greater than the display jump frequency. In this way, it could be considered to jump every minute.

[0048] With reference to the form of execution presented to the Figures 1 and 2, the rotary locking element 7 is a whip in the form of a rod rotatably mounted at its center. The whip is integral with an axial locking pinion 8 for meshing with an intermediate wheel 9 of the finishing gear train. The locking rack 3 is rotatably mounted at a first end opposite the locking part, which comprises the stop pallet 3a. As previously indicated, the rotary locking rack 3 comprises at a second end, the edge portion 3b, which is a finger 3b guided inside a housing made in the cam 6, which is integral with the fixed second wheel SFA 2. This cam 6 formed by two teeth with the housing between the two teeth controls the pivoting of the rack 3, which comprises the locking pallet 3a arranged on a side opposite the finger 3b. As indicated above, this pallet 3a can be made of a hard material reducing friction with the blocking element 7 in contact with the pallet 3a in a stopping phase.

[0049] The pallet 3a is arranged to cooperate in bearing with said blocking element 7, which is a whip, to block said going train in a stop phase, or to release said blocking element 7 and said going train in a jump phase. The whip 7 comprises a first blocking rod portion and a second blocking rod portion relative to its center which comprises the axial locking pinion 8. Once the pallet 3a is no longer in contact with the first rod portion of the whip 7 or the second rod portion of the whip 7, in the jump phase, the whip 7 is rotated and rotates through 180° to allow rotation of the going train before a new blocking position of the going train in a stop mode. In the jump mode, the tourbillon cage 15 is rotated 6° clockwise (SAM) by the going train to add one second to the time.The fixed seconds wheel SFA 2 is driven with the cage 15, which is connected to the coaxial seconds pinion 5 with a 6° angle to rewind the flexible guide 4 of the SFA rack. The fixed seconds wheel SFA 2 is driven by the cage 15, because the escapement mechanism also rotates with the cage. The rewinding of the flexible guide 4 is carried out quickly, which means that the end of the whip 7 returns directly into contact with the stop pallet 3a once the whip 7 has rotated 180°. As soon as this new blockage occurs, a new stop phase operation takes place.

[0050] It is understood that the 180° rotation of the whip 7 before a new stop is directly and dynamically linked to the inertias of the moving components. In particular, the inertia of the whip 7, which has the fastest rotation, is of great importance. A construction of the whip 7 favoring low inertia will therefore be preferred, such as can be obtained with the LIGA manufacturing means in Nickel or Nickel Phosphorus or the DRIE manufacturing means in silicon. These manufacturing means allow the production of whip 7 with precise and advantageous geometry to limit the inertia of the whip 7.

[0051] During the stop phase, the escape wheel 11 is driven in a first direction of rotation (SIAM) by the fixed seconds wheel SFA 2, which corresponds to each half-oscillation of the maintained oscillator 14. 5 small steps are made by the escape wheel 11 driven in rotation by the fixed seconds wheel SFA 2 and via the escape pinion 12. This disarms said flexible guide 4 which drives the fixed seconds wheel SFA 2 and moves said pallet 3a in the direction of release of the whip 7.

[0052] As the going train is blocked in the stop mode with the exception of the fixed seconds wheel SFA 2, the flexible guide 4 linked to the fixed seconds wheel SFA 2 releases energy to rotate said fixed seconds wheel SFA 2 to drive the escape wheel 11. In the jump mode, as soon as the whip 7 is no longer in contact with the pallet 3a, the going train, via the axial locking pinion 8 of the whip 7, is arranged to pivot via the second pinion 5 and the tourbillon cage 15, said fixed seconds wheel SFA 2. This fixed seconds wheel SFA 2 with the tourbillon cage 15 rotates by 6° of angle in a second direction of rotation, which is the clockwise direction (SAM) opposite to said first direction of rotation imposed on the escape wheel 11 by the fixed seconds wheel SFA 2, according to a stroke corresponding to an angular jump of a second.The tourbillon cage 15 is pivoted by 6° of angle in the clockwise jump mode (SAM) in a direction opposite to the pivoting of the fixed seconds wheel SFA 2 in the stop phase. At the end of the jump, the whip 7 returns to rest against the pallet 3a to block the going train again with the exception of the fixed seconds wheel SFA 2. The whip 7 with its two stem parts of the same length rotates by 180° to pass from the jump mode to the next stop mode.

[0053] It should be noted that the whip 7 is linked to the going train and the barrel by the intermediate wheel 9 to rotate it around its central axis at each 1-second jump mode and to release the going train 5, 8, 9, 10, as well as the cage 15 of the tourbillon in this embodiment. The force of the driving spring(s) of the going train is greater than the mechanical energy stored in the flexible guide 4. Thus, the going train is immediately put into operation upon its release, which makes it possible to maintain good synchronism over time, also given that the escapement mechanism and the oscillator 14 are kept in operation during the stopping phase even if the going train is blocked except for the fixed seconds wheel SFA 2.

[0054] All the elements of the force control mechanism described above are mounted on a plate, a middle bridge, a whip bridge, which are not shown so as not to overload the drawings.

[0055] As already mentioned above, the fixed seconds wheel SFA 2 has peripheral teeth meshing with the escapement toothed pinion 12 coaxial with the escape wheel 11. A middle wheel 10, which the finishing gear comprises, has peripheral teeth meshing with the axial second toothed pinion 5 coaxial with the fixed seconds wheel SFA 2, and the axis of the second pinion 5 of which is connected to the tourbillon cage 15. An intermediate wheel 9, which said finishing gear also comprises, has an intermediate axial toothed pinion 19 meshing with the peripheral teeth of the middle wheel 10. The intermediate wheel 9 has peripheral teeth for meshing with said axial locking pinion 8 secured to the rotary locking element 7, which is the whip.In the jump phase when releasing said finishing gear, the intermediate axial toothed pinion 19 is arranged to let the middle wheel 10 rotate, to enable it to pivot the tourbillon cage 15 via the second pinion 5 in said second direction of rotation SAM. In this second direction of rotation, the second pinion 5 provides the energy to be stored in the flexible guide 4 by rotating the fixed second wheel SFA 2 in SAM.

[0056] To determine some dimensional values ​​based on the elements described above, it can be mentioned that the locking is done by a gear train from the middle 10 and a large diameter whip 7. This makes it possible to limit the movement during the second, to limit friction, and to remove the pivoting of the whip 7 from the surface occupied by the tourbillon cage on the plate.

[0057] The high ratio between average 0.116 rpm and whip 0.5 rpm (30 rpm) requires an intermediate wheel, which is intermediate wheel 9. This gives for example a ratio of average wheel 10 to intermediate wheel 9 at Z = 120 / 7 and m = 0.07 mm, and an intermediate wheel 9 to whip 7 at Z = 90 / 6 and m = 0.07 mm.

[0058] According to an alternative version, it is possible to drive the whip 7 from the tourbillon cage 15 directly. This requires producing a tourbillon cage with external teeth meshing with the axial locking pinion 8, which is the whip pinion. The ratio between the cage 15 and the whip 7 is 1 rpm and whip 0.5 rpm (30 rpm), can be achieved with a direct gear train. The external tooth ratio of the tourbillon to the whip pinion is Z = 180 / 6 with m = 0.079 mm with a position of the whip identical to that of the previous version. However, the aesthetics of the tourbillon cage is penalized by this external toothing.

[0059] The resting point (stopping phase) on pallet 3a of rake 3 is 0.08 mm, which is comfortable for an escapement anchor, but probably a little weak compared to the length of the rake. The construction can easily gain 25% by increasing the working radius of pallet 3a. In any case, the increased displacement (for safety) on pallet 3a increases the risks related to friction.

[0060] As a reminder, with reference, for example, to the figure 2, in the stop phase, the finishing train is locked by the support of the whip 7 on the pallet 3a of the rack 3, and the escapement wheel 11 with its escape pinion 12 is driven by the fixed second wheel SFA 2 with the flexible guide 4. In the jump phase, the pallet 3a of the rack 3 releases the finishing train. The second pinion 5 rotates by 6° (one second) and resets the flexible guide 4 for the second wheel 2. The rack 3 of SFA locks the finishing train. The finger 3b of the rack 3 follows the movement of the cam 6 until the pallet 3a is no longer in contact with the end of the whip 7 to release the finishing train. We will not repeat all the other elements already mentioned previously, which are sufficiently clearly shown in the previous figures.

[0061] THE Figures 3a, 3b and 3crepresent three different embodiments of the flexible guide 4, which can be fixed on the one hand under the fixed seconds wheel SFA 2, and on the other hand to a support of the movement, such as a plate. Such embodiments allow for higher torques and better axial support. These three embodiments are also different from the embodiment shown in Figures 1 and 2 and described above.

[0062] On the Figure 3a, we can see the fixed portion 4b and the movable portion 4c of the flexible guide 4, which are both connected by several elastic blades 4a or spring blades, preferably two V-shaped elastic blades. Each of the elastic blades 4a connects a peripheral end of each fixed portion 4b and movable portion 4c. Two through openings 16 are also provided in the fixed portion 4b for fixing on a support of the movement, and two through openings 17 in the movable portion 4c for fixing on the fixed second wheel SFA 2. The position of these through openings 16, 17 is also dependent on the dimension of the fixed second wheel SFA 2 and its fixing parts. The fixed portion 4b also comprises an axial opening 25 for mounting the flexible guide 4 coaxially with the axis of the second pinion 5 and preferably on the axial tube of the fixed second wheel SFA 2.

[0063] On the Figure 3b, we can see a fixed portion 4b and two movable portions 4c each arranged in a respective V-shaped housing of the fixed portion and in symmetrical opposition to each other. The two movable portions 4c are further connected by several elastic blades 4a in connection with an intermediate portion near the axial opening 25 of the flexible guide 4. Two through openings 16 in the fixed portion 4b are made in the most compact portion, and a through opening 17 in each movable portion 4c is made. This structure at the Figure 3b allows the restoring torque and overall rigidity to be increased by adding pairs of blades in parallel.

[0064] Finally on the Figure 3c, a fixed portion 4b can be seen arranged in a wide V-shaped opening housing of the movable portion 4c, which this time includes the axial opening 25. Two through openings 16 are provided in the fixed portion 4b and arranged on the same line with the axial opening 25. Two through openings 17 are provided in the movable portion 4c and arranged practically on the same line with the axial opening 25. In this embodiment, four successive elastic blades 4a connect a first inner side of the movable portion 4c to a first inner side of the fixed portion 4b, where two first elastic blades 4a from the movable portion 4c are connected by a first intermediate central portion, while two second elastic blades 4a from the fixed portion 4c are connected by a second intermediate central portion, the two intermediate blades being connected by a first intermediate peripheral portion.Four successive elastic blades 4a connect a second inner side of the movable portion 4c to a second inner side of the fixed portion 4b, where two first elastic blades 4a from the movable portion 4c are connected by the same first intermediate central portion, while two second elastic blades 4a from the fixed portion 4c are connected by the same second intermediate central portion, the two intermediate blades being connected by a second intermediate peripheral portion. This structure of the . Figure 3c allows to reduce the restoring torque and increase the rotation angle by adding pairs of blades in series.

[0065] It is clear that the type of materials chosen to produce these flexible guides 4 are materials used to produce metal springs. In the different variants of flexible guide 4 described above, each flexible guide 4 can be in the form of a flat plate, in the thickness can be chosen substantially equivalent to the thickness of the central portion of the fixed second wheel SFA 2.

[0066] There figure 4 represents as a complement another schematic embodiment of a traditional mechanical watch movement with the finishing gear train and the force control mechanism according to the invention. Certain elements already described with reference to the Figures 1 and 2are found in this embodiment of the traditional movement, which does not include a tourbillon. But there is an accumulation of energy by a flexible guide 4 with crossed blades 4a connected to a stop member 3 connected to a crown 32 rotatably mounted on the fixed second wheel SFA 2. The flexible guide 4 comprises a fixed base portion, which can be fixed by screws 44 on a watch movement support, and a movable portion which can be directly the crown 32 linked to the stop member 3. The elastic blades 4a are fixed for example by weld points 34 to the crown 32. In this case as previously indicated, the flexible guide 4 must rotate the fixed second wheel SFA 2 with the stop member 3 in the counterclockwise direction (SIAM) in the stopping phase of the movement.

[0067] In this embodiment, the two phases can again be specified, which are on the one hand the stopping phase and on the other hand the jumping phase. In the stopping phase, the finishing gear 5, 8, 9, 10 is locked by the support of a tooth of the blocking element 7 against the stopping member 3. The escape wheel 11 is driven by the fixed seconds wheel SFA 2 in the counterclockwise direction (SIAM) by the action of the flexible guide 4 on the stopping member 3 connected to the fixed seconds wheel SFA 2. In the jumping phase, the stopping member 3 is moved to release the finishing gear. At the same time, the second pinion 5 rotates 6° clockwise (SAM) and drives the crown 53 via the satellite wheels 51, 52 also clockwise, which also allows the flexible guide 4 to be re-armed.As the stop member 3 returns to the blocking position, the stop member 3 again locks the finishing gear for a new operation in the stopping phase to maintain the operation of the escapement mechanism linked to the oscillator.

[0068] Satellite wheels 51, 52 are further mounted in connection with the second pinion 5 coaxial with the second wheel 2. The stop member 3 may be an arcuate plate 3 pivoting about an axis and driven by the flexible guide 4 in this embodiment. In a stop phase, the stop member 3 is in contact with a tooth of a blocking element 7, which comprises in a central portion an axial blocking pinion 8 for driving the intermediate wheel 9 having peripheral teeth. The blocking element 7 may comprise several teeth on its periphery to come into contact with the stop member 3 in the stop phase. In the jump phase, the blocking element 7 is released to rotate through an angle of 120° defining the second jump, as there are 3 blocking teeth.

[0069] In the stopping phase, the escape wheel 11 is driven by the fixed seconds wheel SFA 2 via its coaxial escape pinion 12 meshing with a toothing on the periphery of the fixed seconds wheel SFA 2. At the time of the jump phase, this accumulated energy is supplied to the finishing gear for the jump of the second. The middle wheel 10 driven by the intermediate pinion 19 of the intermediate wheel 9, has a toothing on the periphery to mesh with the coaxial second pinion 5 for the jump of the second. Without direct influence on this jump phase, a large middle wheel 21 has a toothing on the periphery to mesh with a coaxial middle pinion 20.By the action of the second pinion 5, when the finishing gear is in operation, the arrangement by the differential with the satellite wheels 51, 52 and the crown 53 makes it possible to rearm the flexible guide 4 of the SFA to find itself again in the stopping mode with the stopping member 3 blocking the blocking element 7 by one of its teeth.

[0070] It should be noted that the flexible guide 4 with crossed elastic strips 4a is well known. A particular configuration where the strips cross at seven-eighths of their length has already been disclosed in the work of WH Wittrick, "The properties of crossed flexure pivots and the influence of the point at which the strips cross" in The Aeronautical Quarterly II(4), pages 272 to 292 (1951). In addition, pivots with flexible strips are known and described in particular in the work written by Simon Heinein, entitled "Conception des guiders flexibles" and published by PPUR presses polytechniques, in 2001.

[0071] The mobile or second wheel can be pivoted on a ball bearing carried by the plate.

[0072] There Figure 5 shows a cross-section from bottom to top of the mechanism in the center of the tourbillon as shown in part above with reference to the figure 1 or to the figure 2 . We note above all in this figure that the second pinion 5 is the axis of the tourbillon cage 15. The fixed second wheel SFA pivots concentrically to the tourbillon axis without touching it thanks to the flexible blade guide system holding it in position. The tourbillon cage 15 encloses the escapement mechanism with the escapement wheel 11, the Swiss anchor 13 and in connection with the oscillator 14 which is the spiral balance.

[0073] The fixed seconds wheel SFA 2 meshes with the escapement pinion 12, which means that when the tourbillon cage 15 rotates every second, a rotation is also carried out for the escapement mechanism linked to the oscillator and also the fixed seconds wheel SFA 2.

[0074] The flexible guide 4 is fixed to the fixed second wheel SFA 2. To do this, at least one fixing means 27 in or through the openings 17 is thus provided to fix the fixed second wheel SFA 2 to the movable portion of the flexible guide 4 as previously indicated. These fixing means 27 are preferably material extensions of central portions of the second wheel 2 so as to be force-fitted into the openings 17 of the flexible guide 4. These material extensions 27, as well as a border around these material extensions, come directly from the material with the rest of the second wheel to form a single piece.

[0075] As explained previously, a finger-shaped edge portion 3b of the rake 3 is freely arranged inside a guide housing between two teeth of a cam 6 visible at figure 2 . Since the cam 6 is fixed integrally with said fixed second wheel SFA 2 near its center, this makes it possible to rotate the rack 3, which on the other hand comprises the locking pallet 3a for locking the whip 7 in a stop mode. The whip 7 further comprises an axial locking pinion 8, which can be rotated upon release of the whip 7 in the jump mode. All other elements have already been explained above and will not be repeated again.

[0076] From the description which has just been given, multiple variant embodiments of the watch with mechanical movement with force control mechanism and of the jumping second type can be designed by the skilled person without departing from the scope of the invention defined by the claims. The mechanical movement can be a traditional mechanical movement with a fixed second wheel SFA also in connection to drive or maintain the escapement wheel with the oscillator in a stop phase.

Claims

1. Mechanical movement watch (1) with a force control mechanism, and of the jumping seconds type, the force control mechanism being arranged in a going train (5, 8, 9, 10) of the mechanical movement, which is arranged between an energy source and an escape wheel set (11) comprised in an escapement mechanism connected to an oscillator (14) intended to be set in oscillation in normal operation by a drive generated by said energy source to rotate said escape wheel set (11) always in a single direction of rotation at each half-oscillation of the oscillator (14), said escape wheel set (11) meshing with a seconds wheel (2), watch wherein said force control mechanism comprises a rotating locking element (7) arranged to cooperate with a stop member (3) in conjunction with said seconds wheel (2) to lock said going train in a stop mode or release said going train in a jump mode, depending on the angular position of said seconds wheel (2), characterized in that the force control mechanism also comprises : a flexure bearing (4) with elastic strips (4a) attached, on the one hand to the seconds wheel (2), and on the other hand to a support of the watch movement, such as a plate, said flexure bearing (4) with elastic strips (4a) being in a pre-wound state in the stop mode and arranged to drive in rotation the seconds wheel (2) and the escapement mechanism connected to the oscillator (14) at each half-oscillation of the oscillator (14) in the stop mode, and the going train allowing the rotating locking element (7) and a seconds-wheel pinion (5) coaxial to said seconds wheel (2) to rotate in order to make a one-second jump in the jump mode, and also allowing the flexure bearing (4) with elastic strips (4a) to be rewound while allowing the rotating locking element (7) and the going train to be locked for the stop mode following the jump mode.

2. Mechanical movement watch (1) according to claim 1, characterized in that the flexure bearing (4) with elastic strips (4a), once pre-wound, is arranged to gradually move the stop member (3) in the stop mode to a position of release of the rotating locking element (7) at the switch to the jump mode, and to drive in rotation the seconds wheel (2) and to allow the escapement mechanism connected to the oscillator (14) to be driven in the stop mode.

3. Mechanical movement watch (1) according to claim 2, characterized in that the stop member (3) is a rack (3) rotatably mounted about an arbor (33) at a first end and comprising a locking part at a second end, a tooth-shaped edge portion (3b) arranged in a guide housing of a cam (6) fixedly secured to the seconds wheel (2) close to the centre thereof in order to be driven in rotation, and in that a stop piece (3a), such as a pallet stone (3a) at the second end of the locking part, is arranged on a side opposite the edge portion (3b) and arranged to lock the rotating locking element (7) in a stop mode.

4. Mechanical movement watch (1) according to any of the preceding claims, characterized in that the rotating locking element (7) is a flirt (7), which is made by a LIGA or DRIE method.

5. Mechanical movement watch (1) according to any of the preceding claims, wherein the watch is a tourbillon watch, wherein the arbor of a tourbillon carriage (15) containing the escapement mechanism connected to the oscillator (14) is the seconds-wheel pinion (5), characterized in that in the stop mode with the going train (5, 8, 9, 10) locked, the seconds wheel (2) is arranged to drive the escape wheel set (11) in small steps in a first direction of rotation, at each half-oscillation of the oscillator (14) by the action of the flexure bearing (4) with elastic strips (4a) which is pre-wound and attached to the seconds wheel (2), and in that, in the jump mode, when the going train is released, the seconds-wheel pinion (5) is driven by a wheel (10) of the going train to make an angular jump of one second corresponding to the number of small steps made to drive the seconds wheel (2) in the stop mode, in a second direction of rotation opposite to the first direction of rotation, the tourbillon carriage (15), the escapement mechanism with the oscillator (14) and the seconds wheel (2) connected to the escapement mechanism being moved in rotation by an angle of 6° corresponding to one second in the jump mode, and the flexure bearing (4) is rewound to start the successive stop mode with the going train locked.

6. Mechanical movement watch (1) according to claim 5, characterized in that the first direction of rotation is a rotation in the anticlockwise direction, while the second direction of rotation is a rotation in the clockwise direction.

7. Mechanical movement watch (1) according to claim 3, characterized in that the locking element (7) is a flirt (7), which comprises a first locking shaft portion and a second locking shaft portion with respect to the centre thereof which comprises the axial locking pinion (8) so as to make one half-revolution in the jump mode before being locked by the pallet stone (3a) of the rack (3) in the stop mode.

8. Mechanical movement watch (1) according to any of the preceding claims, characterized in that the seconds wheel (2) comprises a peripheral toothing meshing with a toothed escape pinion (12) coaxial to said escape wheel set (11), a medium wheel (10) of the going train having a peripheral toothing meshing with the toothed axial seconds-wheel pinion (5) coaxial to said seconds wheel (2), an intermediate wheel (9) also comprised in said going train comprising an axial toothed intermediate pinion (19) meshing with a peripheral toothing of the medium wheel (10), said intermediate wheel (9) comprising a peripheral toothing for meshing with said axial locking pinion (8) integral with said rotating locking element (7).

9. Mechanical movement watch (1) according to claim 1, characterized in that the escapement mechanism is a Swiss lever escapement mechanism (13) of the mechanical movement, and in that said oscillator (14) is a balance / balance spring intended to be set in oscillation by a drive generated by a mainspring forming said energy source in normal operating mode.

10. Mechanical movement watch (1) according to claim 3, characterized in that the pallet stone (3a) of the rack (3) is made of a hard material, such as ruby, to reduce friction.

11. Mechanical movement watch (1) according to claim 1, characterized in that the flexure bearing (4) comprises at least one fixed portion (4b), at least one movable portion (4c), and elastic strips (4a) connecting the fixed portion (4b) to the movable portion (4c).

12. Mechanical movement watch (1) according to claim 11, characterized in that the fixed portion (4b) is arranged to be secured to a movement support, and in that the movable portion (4c) is arranged to be secured to the seconds wheel (2).

13. Mechanical movement watch (1) according to claim 12, characterized in that the fixed portion (4b) comprises at least one opening (16) for the passage of a means of attachment to the movement support, and in that the movable portion (4c) comprises at least one opening (17) for attaching the seconds wheel (2).

14. Mechanical movement watch (1) according to claim 13, characterized in that the fixed portion (4b) and the movable portion (4c) of the flexure bearing (4) are both connected by several elastic strips (4a), preferably two V-shaped elastic strips (4a), in that each of the elastic strips (4a) connects a peripheral end of each fixed portion (4b) and each movable portion (4c), in that two through openings (16) are provided in the fixed portion (4b) for attachment to a movement support, and in that two through openings (17) are provided in the movable portion (4c) for attachment to the seconds wheel (2).

15. Mechanical movement watch (1) according to claim 13, characterized in that one fixed portion (4b) is provided, whereas two movable portions (4c) are each arranged in a respective V-shaped housing of the fixed portion and symmetrically opposite one another, in that the two movable portions (4c) are also connected by several elastic strips (4a) in conjunction with an intermediate portion close to the axial opening (25) of the flexure bearing (4), in that two through openings (16) are made in the fixed portion (4b) and in that one through opening (17) is made per movable portion (4c).

16. Mechanical movement watch (1) according to claim 11, characterized in that the flexure bearing (4) comprises a fixed portion (4b) arranged in a wide V-shaped housing of the movable portion (4c), which comprises an axial opening (25), in that two through openings (16) are provided in the fixed portion (4b) and arranged on the same line with the axial opening (25), in that two through openings (17) are provided in the movable portion (4c) and arranged practically on the same line with the axial opening (25), in that four successive elastic strips (4a) connect a first inner side of the movable portion (4c) to a first inner side of the fixed portion (4b), wherein two first elastic strips (4a) from the first movable portion (4a) are connected by a first central intermediate portion, whereas two second elastic strips (4a) from the fixed portion (4c) are connected by a second central intermediate portion, the two intermediate strips being connected by a first peripheral intermediate portion, in that four successive elastic strips (4a) connect a second inner side of the movable portion (4c) to a second inner side of the fixed portion (4b), wherein two first elastic strips (4a) from the movable portion (4c) are connected by the same first central intermediate portion, whereas two second elastic strips (4a) from the fixed portion (4c) are connected by the same second central intermediate portion, the two intermediate portions being connected by a second peripheral intermediate portion.

17. Mechanical movement watch (1) according to claim 11, characterized in that the fixed portion (4b) is arranged inside a housing with a wide V-shaped opening in the movable portion (4c), which comprises an axial opening (25), which is coaxial to the axis of seconds-wheel pinion (5), in that two through openings (16) are provided in the fixed portion (4b) and arranged on the same line with the axial opening (25), in that two through openings (17) are provided in the movable portion (4c) and arranged practically on the same line with the axial opening (25), in that five successive elastic strips (4a) connect a first inner side of the movable portion (4c) to a first inner side of the fixed portion (4b), in that a first elastic strip (4a) from the movable portion (4c) is connected to a first central intermediate portion, in that a second elastic strip (4a) from the first central intermediate portion is connected to a first peripheral intermediate portion, in that a third elastic strip (4a) from the first peripheral intermediate portion is connected to a second central intermediate portion, in that a seconds elastic strip (4a) from the second central intermediate portion is connected to a second peripheral intermediate portion, in that a fifth elastic strip from the second peripheral intermediate portion is connected to a second inner side of fixed portion (4a), in that five successive elastic strips (4a) connect a second inner side of the movable portion (4c) to a second inner side of the fixed portion (4b), in that a first elastic strip (4a) from the movable portion (4c) is connected to the same first central intermediate portion, in that a second elastic strip (4a) from the same first central intermediate portion is connected to the same first peripheral intermediate portion, in that a third elastic strip (4a) from the first peripheral intermediate portion is connected to the same second central intermediate portion, in that a fourth elastic strip (4a) from the second central intermediate portion is connected to the same second peripheral intermediate portion, and in that a fifth elastic strip from the same second peripheral intermediate portion is connected to a first inner side of fixed portion (4b).

18. Mechanical movement watch (1) according to claim 1 wherein the watch comprises a conventional mechanical movement without a tourbillon, characterized in that the seconds wheel (2) pivots on the seconds-wheel pinion (5), which is connected by one or two rotating planet wheels (51, 52) to a first crown (53) forming a differential gear not secured to the seconds wheel (2), in that the flexure bearing (4) with crossed elastic strips (4a) is connected to a stop member (3), which is connected to a second crown (32) mounted on the seconds wheel (2) and coaxial to the axis of rotation, in that the flexure bearing (4) comprises a fixed base portion attached by an attachment means (44) to a watch movement support, and a movable portion which can be the second crown (32) itself, connected to the stop member (3), in that the crossed elastic strips (4a) are attached at one end thereof to the second crown (32).

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