EP3502794A1 - Repetition with chain wound onto a cam - Google Patents

Abstract

The repetition mechanism (5) comprises: - a snail (6) hours, - a piece (10) hours carrying a probe (11) hours and mounted in rotation about an axis of hours between a rest position and a reading position, - a spring (19) hours, which recalls the room (10) hours to its reading position, - a pulley (38) rotatably mounted about a pulley axis and which defines a spiral peripheral cam path (39); - a chain (40) adapted to wind on the pulley (38), the chain (40) being hooked on the pulley (38) and on the hour piece (10). and a return spring (35) coupled to the pulley (38) and through which the pulley (140) urges the workpiece (10) through the chain (40) towards its rest position.

Description

FIELD OF THE INVENTION

The invention relates to the field of watchmaking. It concerns, more precisely, a repetition mechanism for a timepiece with a striking ring, the expression "timepiece" preferably designating a watch (with a bracelet or gusset), but which can also designate a clock or a clock clock.

PRIOR ART

The repetitive mechanism (commonly simply called repetition) has the function, on command of the user (or bearer) exerting at any time a pressure on a pusher, to ring the time indicated at this time by the hands of the room d watchmaking.

Repetition is a horological complication of extreme refinement, whose mastery honors the watchmaker who is at the origin. Formerly intended to allow the knowledge of the hour in the darkness, the repetition team nowadays watches of great, even very great value.

• la répétition à minutes, qui, outre les heures, fait tinter toutes les minutes,
• la répétition à quarts, qui, outre les heures, fait tinter le(s) quart(s) écoulé(s) puis les éventuelles minutes résiduelles.

There are several types of repetition. In The Complicated Watches (Ed. Simonin, fifth edition, 2013), F. Lecoultre has five , but essentially distinguishes two (the least rare):

• the repetition in minutes, which, in addition to the hours, makes a noise every minute,
• quarter repetition, which, in addition to the hours, tinkles the quarter (s) elapsed and then any remaining minutes.

• au moins un limaçon des heures,
• au moins une pièce des heures portant un palpeur des heures et montée en rotation autour d'un axe des heures entre :
• une position de repos dans laquelle le palpeur des heures est écarté angulairement du limaçon des heures, et
• une position de lecture dans laquelle le palpeur des heures vient au contact du limaçon des heures,
• un ressort des heures qui rappelle la pièce des heures vers sa position de lecture,
• et un barillet de sonnerie, couplé à la pièce des heures pour la solliciter vers sa position de repos.

Whatever the type, a repeating mechanism typically includes:

• at least a snail of hours,
• at least one hour piece carrying a feeler of the hours and mounted in rotation about an axis of the hours between:
• a rest position in which the hour sensor is angularly spaced from the hours snail, and
• a reading position in which the feeler of the hours comes into contact with the snail of hours,
• a spring of hours which reminds the room of the hours towards its position of reading,
• and a striking barrel, coupled to the hours coin to urge it to its rest position.

In the absence of action of the wearer, the hour room is in its rest position.

The displacement of the pusher causes a forced rotation of the ringer barrel, the hour part being itself moved to its reading position against the spring.

The release of the pusher is accompanied by the return of the room hours to its rest position. Along the way, the hours room meshes (directly or indirectly) a hammer striking a timbre a number of times equal to the number of hours read on the snail and proportional to the angular travel traveled by the hours room between its two positions (reading , rest).

In the so-called ancient repetition, the coupling of the barrel with the hours part was carried out by means of a rocker and a chain, as explained by F. Lecoultre (op.cit., Pp. 68-69 and figure 19 , plate 17).

This coupling has, in modern repetitions, been replaced by a rack and a gear, as also F. Lecoultre (op.cit., Pp.73-74). Two opposing springs are provided: a barrel spring which urges the hours coin to its rest position, and a spring of the hours which urges it towards its reading position. The actuation of the barrel by the wearer, while arming the barrel spring releases the spring hours that reminds the room hours to its reading position. Releasing the barrel unleashes the barrel spring, which recalls the hours coin to its rest position (against the spring of hours), while the hour bell rings.

It has recently been proposed a brand new rehearsal mechanism, which equips the Breguet model 7087 "Tradition" watch, and in which the gear is replaced by a chain transmission.

This transmission is not to be confused with the chain of the ancient repetition mentioned above, because it works in reverse.

• un arbre de barillet,
• un tambour de barillet,
• un ressort de barillet dont une extrémité interne est solidaire de l'arbre de barillet et une extrémité externe est solidaire du tambour de barillet,
• une poulie couplée en rotation à l'arbre de barillet et sur laquelle s'enroule la chaîne.

More precisely, in this repetition, the barrel comprises:

• a barrel tree,
• a barrel drum,
• a barrel spring whose inner end is integral with the barrel shaft and an outer end is integral with the barrel drum,
• a pulley coupled in rotation to the barrel shaft and on which the chain is wound.

The chain is hung, by a proximal end, on the pulley and, by a distal end, on the hour piece. In the absence of action of the wearer on the pusher, the mainspring tends the chain which keeps the hours part in its rest position. The action of the carrier on a pusher causes the forced rotation of the barrel shaft, which frees the chain and therefore the hour piece, which is returned to its reading position by the spring hours.

When the carrier releases the pusher, the mainspring, whose motor torque exerted on the barrel shaft is greater than the resistive torque exerted by the hour spring on the hours part, recalls it to its rest position. On the way, the time is sounded.

Reading (and jingling) quarters and / or minutes follows the same principle, with a snail quarter (respectively minutes) and a quarter piece (respectively minutes) bearing a probe of the quarter (respectively minutes) suitable to come, in a reading position, in contact with the snail quarter (respectively minutes).

This mechanism has an advantage in terms of size and mounting. Indeed, the chain, which is the mechanical link between the cylinder on the one hand and the hour room on the other hand, allows to position them at a distance from one another. It is thus possible, regardless of the positioning of the hour room in the middle, to place the barrel closer to the pusher, which avoids resorting to complex references to levers, to the benefit of the reliability of the watch.

However, slight variations in the frequency of ringing during ringing are noted in this mechanism. It is known to equip the mechanism with a regulator, which makes it possible to compensate for some of these variations. However, a precise measurement shows that despite the regulator the frequency of ringing is not perfectly constant.

A first objective is therefore, in a string repetition mechanism, to further minimize the frequency variations in ringing tones.

A second objective is, more precisely, to minimize the variations in the efforts to which the chain is subjected.

SUMMARY OF THE INVENTION

• un limaçon des heures,
• une pièce des heures portant un palpeur des heures et montée en rotation autour d'un axe des heures entre :
  • une position de repos dans laquelle le palpeur des heures est écarté angulairement du limaçon des heures,
  • une position de lecture dans laquelle le palpeur des heures vient au contact du limaçon des heures,
  • un ressort des heures, qui rappelle la pièce des heures vers sa position de lecture,
  • une poulie montée en rotation autour d'un axe et qui définit un chemin de came périphérique qui s'étend en spirale autour de cet axe,
  • une chaîne apte à s'enrouler partiellement sur la poulie, la chaîne étant accrochée, par une extrémité proximale, sur la poulie et, par une extrémité distale, sur la pièce des heures,
  • un ressort de rappel couplé à la poulie, et par lequel celle-ci sollicite, via la chaîne, la pièce des heures vers sa position de repos.

For this purpose, it is proposed, in the first place, a repetition mechanism for a striking timepiece, which comprises:

• a snail of hours,
• a piece of hours bearing a feeler of the hours and mounted in rotation about an axis of the hours between:
  • a rest position in which the hour sensor is angularly spaced from the hours snail,
  • a reading position in which the feeler of the hours comes into contact with the snail of hours,
  • a spring of the hours, which recalls the room of the hours towards its position of reading,
  • a pulley rotatably mounted about an axis and defining a peripheral cam path that spirals around this axis,
  • a chain adapted to partially wind up on the pulley, the chain being hooked, by a proximal end, on the pulley and, by a distal end, on the hour part,
  • a return spring coupled to the pulley, and by which it requests, via the chain, the hour part to its rest position.

Thanks to the cam path, it is possible to compensate for the variations in the engine torque generated by the mainspring on the cylinder shaft, which makes it possible to minimize the variations in the traction force generated on the chain by the pulley. As a result, during ringing, ringing at extremely regular frequency.

Various additional features may be provided, alone or in combination.

Thus, for example, the pulley and the chain jointly define, on the cam path, a contact point whose distance to the barrel axis decreases with the winding of the chain. In this case, the cam path compensates for the decrease in the engine torque generated by the mainspring.

The variation of the distance from the point of contact to the barrel axis varies in a proportion preferably between 5% and 20%.

The variation of the distance to the axis of the pulley as a function of the winding of the chain is advantageously linear.

• un barillet de sonnerie incluant :
  • un arbre de barillet qui définit un axe de barillet confondu avec l'axe de la poulie,
  • un tambour de barillet,
  • un ressort de barillet dont une extrémité interne est solidaire de l'arbre de barillet et une extrémité externe est solidaire du tambour de barillet,
  • la poulie couplée en rotation au ressort de barillet.

According to a particular embodiment, the repetition mechanism comprises:

• a barrel of ringing including:
  • a barrel shaft which defines a barrel axis coincident with the axis of the pulley,
  • a barrel drum,
  • a barrel spring whose inner end is integral with the barrel shaft and an outer end is integral with the barrel drum,
  • the pulley coupled in rotation to the mainspring.

Second, a timepiece, such as a watch, equipped with a repetition mechanism as presented above, is proposed.

BRIEF DESCRIPTION OF THE FIGURES

• la figure 1 est une vue en perspective montrant partiellement une montre équipée d'un mécanisme de répétition,
• la figure 2 est une vue en perspective du mécanisme de répétition seul, à plus grande échelle,
• la figure 3 est une vue en perspective du mécanisme de répétition, partiellement dénudé pour plus de clarté sur son architecture et son fonctionnement,
• la figure 4 est une vue en perspective du mécanisme de la figure 3, selon un autre angle de vue,
• la figure 5 est une vue en coupe partielle montrant le mécanisme de répétition, selon le plan de coupe V-V de la figure 3,
• la figure 6 est un tracé illustrant la forme du chemin de came,
• la figure 7 est une vue de détail en coupe, dans le même plan que la figure 5, montrant la poulie dans une position de déroulement complet de la chaîne, laquelle est schématisée sous forme d'un trait gras,
• la figure 8 est un diagramme montrant les variations de la distance, au centre de rotation de la poulie, du point de contact avec la chaîne,
• les figures 9, 10 et 11 sont des vues similaires à la figure 8, illustrant l'enroulement progressif de la chaîne sur la poulie.

Other objects and advantages of the invention will become apparent in the light of the description of an embodiment, given hereinafter with reference to the accompanying drawings, in which:

• the figure 1 is a perspective view partially showing a watch equipped with a repetition mechanism,
• the figure 2 is a perspective view of the repetition mechanism alone, on a larger scale,
• the figure 3 is a perspective view of the repetition mechanism, partially stripped for clarity on its architecture and operation,
• the figure 4 is a perspective view of the mechanism of the figure 3 , according to another angle of view,
• the figure 5 is a partial sectional view showing the repetition mechanism, according to the sectional plane VV of the figure 3 ,
• the figure 6 is a plot illustrating the shape of the cam path,
• the figure 7 is a detail view in section, in the same plane as the figure 5 , showing the pulley in a position of complete unfolding of the chain, which is schematized in the form of a bold line,
• the figure 8 is a diagram showing the variations of the distance, at the center of rotation of the pulley, from the point of contact with the chain,
• the figures 9 , 10 and 11 are views similar to the figure 8 , illustrating the progressive winding of the chain on the pulley.

DETAILED DESCRIPTION OF THE INVENTION

On the figure 1 is partially represented a timepiece, in this case a watch 1. The watch 1 comprises a middle part 2 which defines an internal volume 3. In the example shown, the watch 1 is designed for wearing on the wrist, and its caseband 2 comprises for this purpose horns 4 projecting, on which is intended to be fixed a bracelet (not shown).

Watch 1 includes a watch movement designed to indicate at least hours and minutes. The movement comprises a plate intended to be housed in the internal volume 3 defined by the middle part 2, being attached thereto.

The motion further comprises various functional components grouped by subsets. When a subset has a function other than displaying the hours, the minutes and, if necessary, the seconds, it is called "complication".

Thus, the timepiece (that is to say the watch 1) illustrated is ringing, and includes, for the purpose of ringing the current time, a repetition mechanism, also called "repetitive complication" or, more simply (and as used hereinafter), "repetition" 5.

Repetition 5 comprises, in the first place, at least one snail 6 hours. This snail 6 is rotatably mounted on an axis A1. It has a generally spiral shape and comprises on its periphery a succession of twelve angular sectors of decreasing distances to the axis A1.

The snail 6 hours is integral in rotation with a star 7 hours which includes twelve pointed teeth.

In the example shown on the figure 2 , the repetition 5 also comprises a limaçon 8 quarters, rotatably mounted about an axis A2. The quarter lima 8 comprises four angular sectors of decreasing distances to the axis A2, separated by smooth junction faces.

The repetition 5 further comprises a snail 9 minutes, integral in rotation of the quarter snail 8 and which comprises four notched branches on their periphery, separated by smooth junction faces which extend in the extension of the junction faces of the snail 8 quarters.

The quarter snail 8 carries in the vicinity of its periphery a finger which, at each turn, comes to mesh a tooth of the star 7 hours to turn it of a twelfth of a turn representing an advance of one hour.

The repetition 5 comprises, secondly, a part 10 hours, mounted in rotation about an axis A3 and bearing a probe 11 hours.

• une position de repos (en trait plein sur la figure 5) dans laquelle le palpeur 11 des heures est écarté angulairement du limaçon 6 des heures, et
• une position de lecture (en pointillés sur la figure 5) dans laquelle le palpeur 11 des heures vient au contact du limaçon 6 des heures.

The part 10 hours is mounted in rotation about its axis A3 between:

• a rest position (solid line on the figure 5 ) in which the feeler 11 hours is angularly spaced from the snail 6 hours, and
• a reading position (dashed on the figure 5 ) in which the probe 11 hours comes into contact with snail 6 hours.

As illustrated on figure 2 and figure 3 , the part 10 hours comprises a toothed sector 12 coupled to a device 13 of regulation (or regulator) via a gear train 14. In the example shown, the regulator 13 comprises a rotor 15 rotatably mounted in a stator 16.

The regulator 13 is preferably magnetic; it comprises, in this case, a rotor 15 rotatably mounted in a stator 16. The rotor 15 has a limit speed of rotation, determined by an equilibrium between the centrifugal force applied to ferromagnetic movable flyweights mounted on the rotor 15, and a counter-electromotive force generated in the flyweights by eddy currents induced by an alternating magnetic field produced by pairs of magnets provided with the stator 16.

The workpiece 10 hours comprises an outer arm 17 provided with a rake 18 hours, consisting of twelve teeth protruding. During the return of the room 10 hours from its reading position to its rest position, the rake 18 hours activates a hammer hours (not shown) which comes to strike a timbre timed hours at a predetermined acoustic frequency, possibly amplified by a structural part of the watch 1 (eg the middle part 2). The hammer hours strike the hour stamp a number of times (between one and twelve) equal to the number of teeth of the rake 18 which actuated it when returning the play 10 hours from its reading position to its rest position .

Repetition 5 comprises, fourthly, a spring 19 hours, which reminds the room 10 hours to its reading position. In the illustrated example, the spring 19 hours is a spiral spring. It is advantageously fixed on the workpiece 10 hours by an inner end, and on an axis integral with the plate by an outer end 21.

• une position de repos dans laquelle le palpeur 23 des quarts est écarté angulairement du limaçon 8 des quarts, et
• une position de lecture dans laquelle le palpeur 23 des quarts vient au contact du limaçon 8 des quarts.

Repetition 5 comprises, in the example illustrated on the figure 2 , a quarter part 22 bearing a quarter sensor 23 and mounted in rotation about the axis A3 between:

• a rest position in which the feeler 23 of the quarter is angularly spaced from the snail 8 quarters, and
• a reading position in which the feeler 23 quarters comes into contact with the snail 8 quarters.

• une position de repos dans laquelle le palpeur 25 des minutes est écarté angulairement du limaçon 9 des minutes, et
• une position de lecture dans laquelle le palpeur 25 des minutes vient au contact du limaçon 9 des minutes.

The repetition further comprises, in the example illustrated on the figure 2 , a room 24 minutes bearing a probe 25 minutes and mounted in rotation about the axis A3 between:

• a rest position in which the minute sensor 25 is angularly spaced from the snail 9 minutes, and
• a reading position in which the minute sensor 25 comes into contact with snail 9 minutes.

• une position de repos dans laquelle le palpeur 25 des minutes est écarté angulairement du limaçon 9 des minutes, et
• une position de lecture dans laquelle le palpeur 25 des minutes vient au contact du limaçon 9 des minutes.

The repetition further comprises, in the example illustrated on the figure 2 , a room 24 minutes bearing a probe 25 minutes and mounted in rotation about the axis A3 between:

• a rest position in which the feeler 25 of minutes is angularly removed from the snail 9 minutes, and
• a reading position in which the minute sensor 25 comes into contact with snail 9 minutes.

The repetition 5 also includes a quarter spring 26 which recalls the quarter piece 22 towards its reading position, and a minute spring 27 which recalls the minute piece 24 towards its reading position.

The room 24 minutes is provided, on an arm 28 outside, a rake 29 minutes, consisting of fourteen teeth protruding. When returning the play 24 minutes from its reading position to its rest position, the minute rake 29 actuates a minutes hammer (not shown) which hits a minute timbre tuned to a different predetermined acoustic frequency (for example). lower than the acoustic frequency of the hour stamp. The minute hammer strikes the timbre a number of times (between zero and fourteen) equal to the number of rake teeth 29 minutes that actuated it when returning from play 24 minutes of its reading position to his rest position.

The quarter piece 22 is provided, on an outer arm, with a rake 31 of the quarters, consisting of three series of teeth protruding. Upon returning the workpiece 22 quarter of its reading position to its rest position, the quarter rake 31 operates almost simultaneously the hour hammer and the minutes hammer to generate a close sequence of two notes. The hour hammer and the minute hammer strike their respective timbres a number of times (between zero and three) equal to the number of sets of teeth of the rake 31 of the shifts that actuated them when returning from the quarter 22 its reading position at its rest position.

As we see on the figure 2 the workpiece 10 of the hours, the workpiece 22 of the quarters and the workpiece 24 of the minutes, mounted in rotation on the same axis A3, are angularly offset relative to each other, so that, during their rotation solid around axis A3, the readings intervene successively in the following order: minutes; quarters; hours. The ringing is however performed in the reverse order: hours; quarters; minutes.

Repetition 5 comprises, fifth, a barrel 32 ringing.

• un arbre 33 de barillet,
• un tambour 34 de barillet,
• un ressort 35 de barillet dont une extrémité 36 interne est solidaire de l'arbre 33 de barillet et une extrémité 37 externe est solidaire du tambour 34 de barillet, et
• une poulie 38 définit un chemin 39 de came périphérique.

The ringing barrel 32 is rotatably mounted about an axis A4 of the barrel. The ringer barrel 32 is a subset that includes several components, among which:

• a barrel shaft 33,
• a barrel drum 34,
• a barrel spring 35 having an inner end 36 integral with the barrel shaft 33 and an outer end 37 integral with the barrel drum 34, and
• a pulley 38 defines a peripheral cam path 39.

The barrel shaft 33 and the barrel drum 34 are both rotatably mounted about the barrel axis A4.

The pulley 38 is rotatably coupled to the barrel shaft 33. The pulley 38 is mounted around an axis of rotation which is here coincident with the axis A4 of the barrel.

The repetition 5 comprises, sixthly, a chain 40 able to partially wind up on the pulley 38, and more precisely on the path 39 of the cam. The chain 40 is hooked, by a proximal end 41, on the pulley 38 and, by a distal end 42, on the piece 10 hours.

The chain 40 comprises a plurality of links 43 articulated with respect to each other. The link 43 located at the proximal end 41 of the chain 40 is fixed on a pin 44 integral with the pulley 38. The link 43 located at the distal end 42 of the chain 40 is fixed on a pin 45 secured to of the arm 17 outside the room 10 hours.

According to an embodiment illustrated on the Figure 2 to Figure 5 the repetition 5 comprises a return bearing 46 on which the chain 40 passes between the ringer barrel 32 and the hour piece. This bearing 46 of return is advantageously in the form of a bearing (eg ball).

As illustrated on Figure 2 to Figure 4 , the barrel drum 34 carries, on its periphery, a toothed crown 47 with asymmetrical teeth, and the repetition 5 comprises a locking pawl 48 engaged with this toothed crown 47, to block the rotation of the barrel drum 34 in the direction unwinding of the chain 40.

• une crémaillère 49 montée en rotation autour d'un axe A5 de crémaillère fixe, et pourvue d'un secteur 50 denté,
• un rouage 51 de sonnerie en relation d'engrenage d'une part avec la crémaillère 49 et d'autre part avec l'arbre 33 de barillet.

As shown on the figure 4 , repetition 5 includes, in seventh place:

• a rack 49 rotatably mounted about a fixed rack axis A5, and provided with a sector 50 toothed,
• a gear wheel 51 in gear relationship on the one hand with the rack 49 and on the other hand with the shaft 33 of the barrel.

The rack 49 has a hook shape. The rack 49 is provided with a bore 52 through which it is mounted on its axis A5. On either side of this bore 52, the rack 48 comprises a lever 53 carrying at its end a button 54 (which, in the example shown, is attached and driven into a hole formed in the end of the lever 53), and an arm 55 bent in which is formed the toothed sector 50.

The rack 49 is rotatably mounted about its axis A5 between a rest position ( figure 4 ) and a complete arming position.

According to an embodiment illustrated on the figure 4 , the gear wheel 51 includes an input gear 56 meshing with the rack 49, and an output pinion 57 integral in rotation with the shaft 33 of the barrel.

In the example shown, the ring gear wheel 51 further comprises a gear 58 multiplier (partially torn off the figure 4 ) integral in rotation with the input gear 56 and meshing with the output gear 57.

As we also see on the figure 4 , the rack 49 is advantageously provided, at the free end of the toothed sector 50, with an abutment stop 59, which is here in the form of a driven insert, and which, in the fully armed position of the rack 49, is wedged against the input gear 56 which thus forms a limit stop for it.

• une position désarmée dans laquelle le poussoir 60 n'exerce pas de couple moteur sur la crémaillère 49, et
• une position d'armement dans laquelle le poussoir 60 exerce sur la crémaillère 49, via le bouton 54, une poussée (indiquée par la flèche blanche en bas à gauche sur la figure 4 et en bas à droite sur la figure 5) générant un couple moteur qui entraîne en rotation l'arbre 33 de barillet via le rouage 51 de sonnerie.

As illustrated on the figure 1 the watch 1 is equipped with a pusher 60. This pusher 60 is mounted in translation relative to the middle part 2 between:

• a disarmed position in which the pusher 60 does not exert a motor torque on the rack 49, and
• an arming position in which the pusher 60 exerts on the rack 49, via the button 54, a thrust (indicated by the white arrow in the lower left on the figure 4 and bottom right on the figure 5 ) generating a motor torque that rotates the barrel shaft 33 via the wheel gear 51.

The actuation of the repetition 5 is effected by pressing the finger on the pusher 60. The pusher 60 pushes the button 54 which, via the lever 53, rotates the rack 49 about its axis A5. The rack 49 drives in rotation, by meshing with its toothed sector 50, the input gear 56, which rotation the multiplier pinion 58, integral with the latter, transmits to the output gear 57, which drives in its rotation the barrel shaft 33 (in the direction of arrow F1 on the figure 5 ) with the pulley 38 which is integral with it. The forced rotation of the rack 49 and the parts that it drives is done against the return torque imposed by the mainspring spring 35, the inner end 36 of which rotates with the barrel shaft 33 while the external end 37 remains fixed with the barrel drum 34 blocked by the pawl 48 in engagement with the ring gear 47 toothed. It will be understood, therefore, that the rotation of the rack 49 has the effect of cocking the barrel spring.

The chain 40, drawn (in the direction of the arrow F2 on the figure 5 ) at its distal end 42 end by the hour piece, itself revolved (in the direction of the arrow F3 on the figure 5 ) to its reading position by spring 19 hours, unwind pulley 38.

Having arrived at the reading position, in which the hour sensor 11 comes into contact with the snail 6 hours, the room 10 hours is stopped, while, where appropriate, the room 22 of the quarters and the room 24 minutes can continue their rotation, respectively biased towards their reading positions by the spring 26 of the quarters and the spring 27 of the minutes, until the feeler 23 of the quarters and the feeler 25 of the minutes reach the contact, respectively, of the quarterfin 8 and the 9th minute snail.

The release of the pusher 60 frees the barrel spring 35, whose outer end 37 remains fixed with the barrel drum 34 and whose inner end 36 rotates the barrel shaft 33 (in the opposite direction to the arrow). F1) and with it the pulley 38 (in the same direction of rotation). As the restoring moment imposed on the pulley by the mainspring spring is greater (or even much greater) than the resisting torque opposed to the workpiece 10 hours by the spring 19 hours, the pulley 38 draws (in the opposite direction to the arrow F2) the chain 40 which is wound therein by carrying with it the part 10 hours rotating about its axis A3 (in the opposite direction to the arrow F3), until the room 10 hours reaches its rest position, to which it comes by abutting against the bearing 46 of return, which blocks the repetition 5.

During the race accompanying the release of the pusher 60, the room 10 hours, the room 22 of the quarters and the room 24 minutes have together (and in the manner explained above) sounded the time displayed.

This is so that the ringing is performed at a frequency as regular as possible that the repetition 5 is provided with the regulator 13.

However, the regulator 13 is not sufficient, since it turns out that the engine torque, denoted C, induced on the barrel shaft 33 by the barrel spring 35, is not constant according to the angular position, denoted A pulley 38, measured by reference to the arming position (for which, by convention, A = 0). In the following, this angular position A is called "Pulley angle".

As we see on the figure 2 to the figure 5 , the chain 40 has a straight section 40.1, which extends between the pulley 38 and the return bearing 46, and a curvilinear section 40.2, wound on the pulley 38 (and more exactly on the path 39 of cam) in the extension from section 40.1 right.

The pulley 38 and the chain 40 together define, on the path 39 of cam, a contact point M. This point M of contact is located at the limit of the winding of the chain 38.

The point M of contact is the point of the path 39 of cam where the chain 40 begins its winding on the pulley 38 or, which amounts to the same, the point where the chain 40 leaves the pulley 38. In other words, the M point of contact is located at the junction between the 40.1 straight section and the 40.2 curvilinear section. Depending on the angular position of the pulley 38, the location of the point M on the cam path 39 moves.

The engine torque C is transmitted by the barrel shaft 33 to the pulley 38, which is coupled to it in rotation about the barrel axis A4. The pulley 38 in turn, due to the engine torque C generated by the mainspring 35, has a tensile force, denoted T. This tensile force T is applied to the point M of contact, in the axis of the section. 40.1 right. We denote L and called "lever" the distance from the contact point M to the barrel axis A4.

Given these ratings, the tensile force T is deduced from the torque C by the following conventional formula: $$T=\frac{C}{\mathrm{The}}$$

Since the engine torque C is not constant along the pulley angle A, it follows that, if the lever L were constant, the traction force T would not be constant either according to the pulley angle A.

This is the function of the cam path 39: to vary the lever L to compensate for the variation of the torque C and thus to minimize the variations of the traction force T.

More specifically, it has been found that the engine torque C decreases as the pulley angle A increases, starting from the disarmed position (illustrated in FIG. figure 7 ).

This is why the cam path 39 extends spirally about the barrel axis A4. More specifically, the lever L decreases with the winding of the chain 40 (that is to say, as the pulley angle A increases). In other words, the distance to the barrel axis A4 from the contact point M is a decreasing function of the pulley angle A.

We drew on the figure 8 a curve representing the variations of the lever L (placed on the ordinate, whose axis is graduated in millimeters in the example illustrated) as a function of the pulley angle A (placed on the abscissa, whose axis is graduated in degrees in the illustrated example). Li is noted the lever (called "initial") measured when the pulley angle A is zero (in the disarmed position corresponding to the unwinding of the pulley 38, figure 8 ) and Lf the lever (called "final") measured when the angle A is maximum (in the armed position corresponding to the total winding of the pulley 38, figure 11 ).

The lever L preferably varies in a proportion of between 5% and 20%. This variation may seem small, but it is sufficient to compensate for variations in the engine torque C and make the traction T exerted on the chain 40 by the pulley 38 urged by the mainspring 35 more or less constant.

$$\mathrm{Lf}\cong 3,30\mathrm{mm}$$

In a particular embodiment: $$\mathrm{Li}\cong 3,85\mathrm{mm}$$

$$\mathrm{Lf}\cong 3,30\mathrm{mm}$$

The variation of the lever L is therefore, in this example, about 14% but this example can not be limiting because it depends on the performance of the spring 35.

As already suggested, a deformed spring tends to resume a stable equilibrium configuration by generating a restoring torque which is not constant according to its deformation. A more precise examination shows that, in general, the variation of the return torque generated by a spring as a function of its deformation is not generally linear but can be locally.

It is thus understood that if it is possible to maintain the spring 35 in a deformation range where the variation of the generated torque is linear, it is possible to design a pulley 39 whose lever L also varies linearly as a function of the angle A pulley. In other words, the cam path 39 is spiral Archimedean.

So, in the example shown on the figure 8 , a curve is shown the variation of the lever L as a function of the pulley angle A. It can be seen that, in this example, the lever L varies linearly as a function of the pulley angle A, which corresponds to an Archimedean spiral cam path 39.

An example of construction of the cam path 39 is illustrated in the drawings, and more particularly on the figure 6 . In this example, the cam path 39 extends over an angular sector S whose amplitude is less than 360 ° (i.e., the cam path 39 is intended to perform its function on less than 60 °. a pulley turn 38 around the barrel axis A4.

In the example shown on the Figures 7 to 10 , who corresponds to a pulley whose variations of the lever L are illustrated on the figure 6 the amplitude of the angular travel of the pulley 38 is about 270 °.

• minimisation des variations de la fréquence (c'est-à-dire du nombre de tintements par seconde - ou par minute) des tintements de sonnerie,
• minimisation des variations des efforts dans la chaîne. On peut noter que cela a notamment pour conséquence de limiter la fatigue mécanique dans la chaîne, et donc d'augmenter sa durée de vie.

The benefits of this architecture have already been mentioned; we recall them:

• minimizing variations in the frequency (i.e., the number of ringings per second - or minute) of ringing tones,
• minimizing the variations of the forces in the chain. It may be noted that this has the particular consequence of limiting the mechanical fatigue in the chain, and therefore of increasing its service life.

It will be noted that the architecture which has just been described may admit variants without departing from the scope of the invention.

Thus, it is conceivable to replace the cylinder 32 with another subassembly having the same motor function. Such a subassembly comprises, for example, a bending-beam spring, to which the pulley 38 is coupled by means of one or more connecting pieces transforming the bending movement of the spring-beam into rotational movement of the beam. pulley 38. The function of such a beam-spring is the same as that of the mainspring 35: to urge, via the pulley 38 and the chain 40, the workpiece 10 hours towards its rest position.

Claims (6)

Mechanism (5) for repetition for a striking timepiece (1), which comprises: - a snail (6) hours, a piece (10) of hours carrying a feeler (11) hours and mounted in rotation about an axis (A1) hours between: - A rest position in which the probe (11) hours is angularly spaced from the snail (6) hours, - A reading position in which the probe (11) hours comes into contact with the snail (7) hours, - a spring (19) hours, which reminds the room (10) hours to its reading position, a pulley (38) rotatably mounted about a pulley axis (A4), a chain (40) able to partially wind up on the pulley (38), the chain (40) being hooked, by a proximal end (41), on the pulley (38) and, by a distal end (42) , on the piece (10) hours, - a return spring (35) coupled to the pulley (38), and by which the latter requests, via the chain (40), the workpiece (10) hours towards its rest position, characterized in that the pulley (38) defines a peripheral cam path (39) which spirals around the pulley axis (A4). Mechanism (5) according to claim 1, wherein the pulley (38) and the chain (40) jointly define, on the cam path (39), a contact point (M) whose distance (L) to the barrel axis (A4) decreases with the winding of the chain (38). Mechanism (5) according to claim 1 or claim 2, wherein the variation of the distance (L) to the pulley axis (A4) as a function of the winding of the chain (38) is linear. Mechanism (5) according to one of claims 2 and 3, wherein the variation of the distance (L) from the point (M) of contact to the axis (A4) cylinder varies between 5% and 20% % Repetition mechanism (5) according to one of the preceding claims, which comprises: - a barrel (32) of ringing including: a barrel shaft (33) defining an axis (A4) of a barrel coincident with the axis (A4) of the pulley, a barrel drum (34), a spring (35) of a barrel, one end (36) of which is integral with the barrel shaft (33), and one end (37) of which is integral with the drum (34) of the barrel, and - The pulley (38), coupled in rotation to the spring (35) of the barrel. Timepiece (1), such as a watch, equipped with a mechanism (5) for repetition according to one of the preceding claims.

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