CH714504A2 - Rewind mechanism with a chain wound on a cam for a timepiece with a bell. - Google Patents

Abstract

The repetition mechanism (5) for a striking timepiece comprises: a snail of the hours, a workpiece (10) of the hours carrying a feeler of the hours and mounted in rotation about an axis of the 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 path ( 39), a chain (40) adapted to wind on the pulley (38), the chain (40) being hooked on the pulley (38) and on the piece (10) hours, and a return spring coupled to the pulley (38), and by which the latter requests, via the chain (40), the workpiece (10) hours towards its rest position. According to the invention, the pulley defines a peripheral cam path which spirals around the axis of the pulley.

Description

FIELD OF THE INVENTION The invention relates to the field of watchmaking. More specifically, it relates to a repetition mechanism for a striking timepiece, the expression “timepiece” preferably designating a watch (with bracelet or pocket), but which can also designate a pendulum or else a clock.

PRIOR ART [0002] The repetition mechanism (commonly simply called repetition) has the function, at the command of the user (or wearer) exerting pressure on a push-button at any time, to strike the time indicated at this instant by the hands of the timepiece.

Repetition is a watchmaking complication of extreme refinement, the mastery of which honors the watchmaker who created it. Formerly intended to allow the knowledge of the hour in the dark, repetition equips today watches of great, even very great value.

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

- the minute repeater, which, apart from the hours, makes it ring every minute,

- the quarter repetition, which, apart from the hours, causes the quarter (s) past (s) to ring, then any remaining minutes. Whatever the type, a repeating mechanism conventionally includes:

- at least one hour snail,

- at least one hour piece carrying an hour sensor and rotatably mounted around an hour axis between:

- a rest position in which the hour feeler is angularly moved away from the hour snail, and

- a reading position in which the hour sensor comes into contact with the hour snail,

- an hour spring which brings the hour piece back to its reading position,

- and a striking barrel, coupled to the hour piece to urge it towards its rest position.

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

The movement of the pusher causes a forced rotation of the striking barrel, the hour piece itself being moved towards its reading position against the spring.

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

In the so-called ancient repetition, the coupling of the barrel to the hour piece was effected 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 rehearsals, been replaced by a rack and a train, as also explained by F. Lecoultre (op.cit., Pp.73-74). Two opposing springs are provided: a barrel spring which urges the hour piece to its rest position, and an hour spring which urges it towards its reading position. The actuation of the barrel by the wearer, while arming the barrel spring, releases the hour spring which brings the hour piece back to its reading position. Releasing the barrel, on the contrary, releases the barrel spring, which brings the hour piece back to its rest position (against the hour spring), while the hour strike takes place.

It has recently been proposed a completely new repetition mechanism, which equips the Breguet watch model 7087 "Tradition", and in which the cog 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.

More precisely, in this repetition, the barrel comprises:

- a barrel tree,

- a barrel drum,

- a barrel spring, one internal end of which is secured to the barrel shaft and one outer end of which is secured to 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 hours piece. In the absence of action by the wearer on the pusher, the barrel spring tightens the chain which keeps the hours piece in its rest position. The action of the wearer on a pusher causes the barrel shaft to rotate forcibly, which frees the chain and therefore the hours piece, which is returned to its reading position by the hours spring.

CH 714 504 A2 When the wearer releases the plunger, the barrel spring, whose driving torque exerted on the barrel shaft is greater than the resistant torque exerted by the hour spring on the hour piece, recalls this one this towards its rest position. Along the way, the hour has come.

The reading (and the tinkling) of the quarters and / or the minutes follows the same principle, with a snail of the quarters (respectively of the minutes) and a part of the quarters (respectively of the minutes) carrying a feeler of the quarters (respectively of the minutes) able to come, in a reading position, into contact with the snail of the quarters (respectively of the minutes).

This mechanism has an advantage in terms of size and mounting. Indeed, the chain, which makes the mechanical link between the barrel on the one hand and the hour piece on the other hand, allows them to be positioned at a distance from each other. It is thus possible, whatever the positioning of the hours piece in the middle, to place the barrel as close as possible to the pusher, which avoids having to resort to complex lever references, to the benefit of the reliability of the shows.

However, we note in this mechanism slight variations in the frequency of tinkling when ringing. It is known to equip the mechanism with a regulator, which makes it possible to compensate for part of these variations. However, an accurate measurement shows that despite the regulator the frequency of tinkling is not perfectly constant.

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

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

SUMMARY OF THE INVENTION For this purpose, it is proposed, firstly, a repetition mechanism for a striking timepiece, which comprises:

- an hour snail,

- an hour piece carrying an hour sensor and rotatably mounted around an hour axis between:

- a rest position in which the hour feeler is angularly moved away from the hour snail,

- a reading position in which the hour sensor comes into contact with the hour snail,

- an hour spring, which brings the hour piece back to its reading position,

- a pulley rotatably mounted around an axis and which defines a peripheral cam path which extends in a spiral around this axis,

- a chain capable of being partially wound on the pulley, the chain being hooked, by a proximal end, on the pulley and, by a distal end, on the hours piece,

- a return spring coupled to the pulley, and by which the latter urges, via the chain, the hour piece towards its rest position.

Thanks to the cam path, it is possible to compensate for the variations in the motor torque generated by the barrel spring on the barrel shaft, which makes it possible to minimize the variations in the tensile force generated on the chain by pulley. This results in ringing at extremely regular frequency.

Various additional characteristics can be provided, alone or in combination.

Thus, for example, the pulley and the chain jointly define, on the cam track, a contact point whose distance to the barrel axis decreases with the winding of the chain. In this case, the cam path makes it possible to compensate for the reduction in the motor torque generated by the barrel spring.

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

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

According to a particular embodiment, the repetition mechanism comprises:

- a ring barrel including:

- a barrel shaft which defines a barrel axis coincident with the axis of the pulley,

- a barrel drum,

- a barrel spring, one internal end of which is secured to the barrel shaft and one outer end of which is secured to the barrel drum,

- the pulley coupled in rotation to the barrel spring.

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

CH 714 504 A2

BRIEF DESCRIPTION OF THE FIGURES Other objects and advantages of the invention will appear in the light of the description of an embodiment, given below with reference to the appended drawings in which:

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

DETAILED DESCRIPTION OF THE INVENTION In FIG. 1 is partially shown a timepiece, in this case a watch 1. Watch 1 comprises a middle part 2 which defines an internal volume 3. In the example illustrated, watch 1 is designed for wearing on the wrist, and its middle 2 includes for this purpose protruding horns 4, on which is intended to be attached a bracelet (not shown).

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

The movement also includes various functional components grouped by subsets. When a subset has a function other than displaying the hours, minutes and, if applicable, seconds, it is called a "complication".

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

The repetition 5 comprises, first of all, at least one snail 6 of the hours. This snail 6 is mounted in rotation on an axis A1. It has a general spiral shape and includes on its periphery a succession of twelve angular sectors with decreasing distances to the axis A1.

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

In the example illustrated in fig. 2, the repetition 5 also includes a snail 8 of the quarters, mounted in rotation about an axis A2. The snail 8 of the quarters comprises four angular sectors of decreasing distances to the axis A2, separated by smooth joining faces.

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

The snail 8 of the quarters carries in the vicinity of its periphery a finger which, at each turn, engages a tooth of the 7 o'clock star to rotate the latter by a twelfth of a turn representing an advance of one o'clock.

The repetition 5 comprises, secondly, a part 10 of the hours, rotatably mounted around an axis A3 and carrying a probe 11 of the hours.

The 10 hour part is rotatably mounted around its axis A3 between:

a rest position (in solid lines in FIG. 5) in which the feeler 11 for the hours is angularly moved away from the snail 6 for the hours, and

CH 714 504 A2

- a reading position (dotted in Fig. 5) in which the 11 hour probe comes into contact with the 6 hour snail.

As illustrated in FIGS. 2 and fig. 3, the part 10 of the hours comprises a toothed sector 12 coupled to a device 13 for regulation (or regulator) via a gear train 14 for transmission. In the example illustrated, 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 rotational speed, determined by a balance between the centrifugal force applied to mobile ferromagnetic weights mounted on the rotor 15, and a counter-electromotive force generated in the counterweights by eddy currents induced by an alternating magnetic field produced by pairs of magnets with which the stator 16 is provided.

The part 10 of the hours includes an outer arm 17 provided with a rake 18 of the hours, consisting of twelve projecting teeth. When the hour piece 10 returns from its reading position to its rest position, the hour rake 18 operates an hour hammer (not shown) which strikes an hour stamp tuned to a predetermined acoustic frequency, possibly amplified by a structural part of watch 1 (e.g. middle part 2). The hour hammer strikes 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 the 10 hour piece returned from its reading position to its position. rest.

The repetition 5 comprises, in the fourth place, a spring 19 for the hours, which recalls the part 10 for the hours towards its reading position. In the example illustrated, the hour spring 19 is a spiral spring. It is advantageously fixed to the part 10 of the hours by an internal end 20, and on an axis integral with the plate by an external end 21.

The repetition 5 comprises, in the example illustrated in FIG. 2, a part 22 of the quarters carrying a probe 23 of the quarters and mounted in rotation around the axis A3 between:

a rest position in which the probe 23 of the quarters is angularly separated from the snail 8 of the quarters, and

- A reading position in which the probe 23 of the quarters comes into contact with the snail 8 of the quarters.

The repetition further comprises, in the example illustrated in FIG. 2, a 24-minute part carrying a 25-minute probe and rotatably mounted around the A3 axis between:

a rest position in which the feeler 25 of the minutes is angularly moved away from the snail 9 of the minutes, and

a reading position in which the probe 25 for the minutes comes into contact with the snail 9 for the minutes.

The repetition further comprises, in the example illustrated in FIG. 2, a 24-minute part carrying a 25-minute probe and rotatably mounted around the A3 axis between:

a rest position in which the feeler 25 of the minutes is angularly moved away from the snail 9 of the minutes, and

a reading position in which the probe 25 for the minutes comes into contact with the snail 9 for the minutes.

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

The part 24 of the minutes is provided, on an outer arm 28, with a rake 29 of the minutes, consisting of fourteen projecting teeth. When the 24-minute piece returns from its reading position to its rest position, the 29-minute rake operates a minute hammer (not shown) which strikes a timbre of the minutes tuned to a different predetermined acoustic frequency (by e.g. lower) than the acoustic frequency of the hour stamp. The hammer of the minutes strikes the timbre of the minutes a number of times (between zero and fourteen) equal to the number of teeth of the rake 29 of the minutes which actuated it when returning the piece 24 minutes from its reading position to its rest position.

The part 22 of the quarters is provided, on an outer arm 30, with a rake 31 of the quarters, consisting of three series of projecting teeth. When the part 22 of the quarters returns from its reading position to its rest position, the rake 31 of the quarters actuates the hammer of the hours and the hammer of the minutes almost simultaneously to generate a close sequence of two notes. The hammer of the hours and the hammer of the minutes 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 quarters which actuated them during the return of the piece 22 of the quarters of its reading position to its rest position.

As seen in FIG. 2, the part 10 for the hours, the part 22 for the quarters and the part 24 for the minutes, mounted in rotation on the same axis A3, are angularly offset with respect to each other, so that, when they are integral rotation around axis A3, the readings occur successively in the following order: minutes; quarters; hours. The ringing is however carried out in the reverse order: hours; quarters; minutes.

The repetition 5 comprises, fifthly, a ringing barrel 32.

The ringing barrel 32 is mounted for rotation about an axis A4 of the barrel. The ringing barrel 32 is a sub-assembly which comprises several components, among which:

- a barrel shaft 33,

- a barrel drum 34,

CH 714 504 A2

a barrel spring 35, one internal end 36 of which is integral with the barrel shaft 33 and one external end 37 of which is integral with the barrel drum 34, and

- A pulley 38 defines a path 39 of peripheral cam.

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

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

The repetition 5 comprises, in sixth place, a chain 40 capable of being partially wound on the pulley 38, and more precisely on the cam track 39. The chain 40 is hooked, by a proximal end 41, on the pulley 38 and, by a distal end 42, on the part 10 of the hours.

The chain 40 includes 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 secured to the pulley 38. The link 43 located at the distal end 42 of the chain 40 is fixed on a pin 45 secured of the arm 17 outside of the part 10 of the hours.

According to an embodiment illustrated in FIGS. 2 to fig. 5, the repetition 5 comprises a return bearing 46 on which the chain 40 circulates, between the striking barrel 32 and the hour piece 10. This return bearing 46 is advantageously in the form of a bearing (for example with balls).

As illustrated in FIGS. 2 to fig. 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 of chain unwinding 40.

As shown in FIG. 4, the repetition 5 comprises, in seventh place:

- a rack 49 rotatably mounted about an axis A5 of a fixed rack, and provided with a toothed sector 50,

- A ring gear 51 in relation to the gear on the one hand with the rack 49 and on the other hand with the barrel shaft 33.

The rack 49 has a hook shape. The rack 49 is provided with a bore 52 by 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 illustrated, is attached and driven into a hole formed in the end of the lever 53) , and a bent arm 55 in which the toothed sector 50 is formed.

The rack 49 is rotatably mounted around its axis A5 between a rest position (fig. 4) and a fully cocked position.

According to an embodiment illustrated in FIG. 4, the ringing train 51 comprises a pinion 56 of input meshing with the rack 49, and a pinion 57 of output integral in rotation with the shaft 33 of the barrel.

In the example illustrated, the ringing train 51 further comprises a multiplier pinion 58 (partially cut away in FIG. 4) integral in rotation with the input pinion 56 and meshing with the output pinion 57.

As can also be seen in FIG. 4, the rack 49 is advantageously provided, at the free end of the toothed sector 50, with a stopper 59, which is here in the form of a driven insert, and which, in the fully cocked position of the rack 49, is wedged against the input pinion 56 which thus forms an end of travel stop for the latter.

As illustrated in FIG. 1, 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 engine 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 at the bottom left in fig. 4 and at the bottom right in fig. 5) generating a motor torque which rotates the barrel shaft 33 via the ringing train 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 rotates, by meshing its toothed sector 50, the input pinion 56, rotation that the multiplier pinion 58, integral with the latter, transmits to the output pinion 57, which drives in its rotation the barrel shaft 33 (in the direction of arrow F1 in FIG. 5) with the pulley 38 which is integral with it. The forced rotation of the rack 49 and the parts which it drives takes place against the return torque imposed by the barrel spring 35, the internal end 36 of which rotates with the barrel shaft 33 while the end 37 external remains fixed with the barrel drum 34 blocked by the pawl 48 engaged with the toothed crown 47. It is therefore understood that the rotation of the rack 49 has the effect of arming the barrel spring 35.

The chain 40, towed (in the direction of the arrow F2 in FIG. 5) on the side of its distal end 42 by the part 10 of the hours, itself recalled in rotation (in the direction of the arrow F3 in Fig. 5) towards its reading position by the hour spring 19, takes place from the pulley 38.

CH 714 504 A2 Having reached the reading position, in which the 11 o'clock feeler comes into contact with the 6 o'clock snail, the 10 o'clock part is stopped, while, if necessary, the 22 part of the quarters and the piece 24 of the minutes can continue their rotation, respectively returned to 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 snail 8 of the quarters and of the snail 9 of the minutes.

The release of the plunger 60 releases the barrel spring 35, the outer end 37 of which remains fixed with the barrel drum 34 and the inner end 36 of which rotates the barrel shaft 33 (in the opposite direction arrow F1) and with it the pulley 38 (in the same direction of rotation). As the return torque imposed on the pulley by the barrel spring 35 is greater (or even much greater) than the resistive torque opposed to the part 10 of the hours by the hour spring 19, the pulley 38 tows (in the opposite direction to the arrow F2) the chain 40 which is wound therein carrying with it the piece 10 of the hours in rotation about its axis A3 (in the direction opposite to the arrow F3), until the piece 10 of the hours reaches its rest position, which it achieves by coming up against the return bearing 46, which blocks repetition 5.

During the race accompanying the release of the pusher 60, the part 10 for the hours, the part 22 for the quarters and the part 24 for the minutes, together (and as explained above) rang the time displayed.

It is so that the ringing is carried out at a frequency as regular as possible that the repetition 5 is provided with the regulator 13.

However, the regulator 13 is not sufficient, because 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, of the pulley 38, measured by reference to the arming position (for which, by convention, A = 0). In what follows, the angular position A is called “Pulley angle”.

As seen in FIG. 2 in fig. 5, the chain 40 has a straight section 40.1, which extends between the pulley 38 and the return bearing 46, and a curved section 40.2, wound on the pulley 38 (and more precisely on the cam track 39) in the extension of section 40.1 right.

The pulley 38 and the chain 40 jointly define, on the cam path 39, a point M of contact. 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 cam path 39 where the chain 40 begins its winding on the pulley 38 or, which amounts to the same thing, the point where the chain 40 leaves the pulley 38. In others terms, the contact point M is located at the junction between the straight section 40.1 and the curved section 40.2. Depending on the angular position of the pulley 38, the location of 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 exerts, due to the motor torque C generated by the barrel spring 35, a tensile force, noted 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 we call "lever" the distance from point M of contact to the barrel axis A4.

Given these ratings, the tensile force T is deduced from the torque C by the following conventional formula:

As the engine torque C is not constant along the angle of the pulley, it follows that, if the lever L was constant, the tensile force T would not be constant either according to the angle A pulley.

This is the function of the cam track 39: varying the lever L to compensate for the variation in the torque C and thus minimizing the variations in the tensile force T.

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

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

We have drawn in FIG. 8 a curve representing the variations of the lever L (placed on the ordinate, the axis of which is graduated in millimeters in the example illustrated) as a function of the angle A of pulley (placed on the abscissa, the axis of which is graduated in degrees in the example shown). We note Li the lever (called "initial") measured when the angle A of pulley is zero (in the disarmed position corresponding to the unwinding of pulley 38, fig. 8) and Lf the lever (said "final") measured when l angle A is maximum (in the armed position corresponding to the total winding of the pulley 38, fig. 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 the variations in the engine torque C and allow the traction T exerted on the chain 40 by the pulley 38 recalled by the barrel spring to be made more or less constant.

CH 714 504 A2 In a particular embodiment:

Li = 3.85 mm

Lf = 3.30 mm The variation of the lever L is therefore, in this example, around 14% but this example cannot be limiting since it depends on the performance of the spring 35.

As has already been 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 restoring torque generated by a spring as a function of its deformation is generally not linear but can be locally.

It is therefore understood that if one can maintain the spring 35 in a range of deformation 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 of pulley. In other words, Cam Track 39 is an Archimedean spiral.

Thus, in the example illustrated in FIG. 8, the curve L shows the variation of the lever L as a function of the angle A of the pulley. It can be seen that, in this example, the lever L varies linearly as a function of the angle A of pulley, which corresponds to a path 39 of an Archimedes' spiral cam.

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

In the example illustrated in FIGS. 7 to 10, which corresponds to a pulley, the variations of the lever L of which are illustrated in FIG. 6, the amplitude of the angular stroke of the pulley 38 is approximately 270 °.

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

- minimization of the variations in the frequency (i.e. the number of tingles per second - or per minute) of ringing tones,

- minimization of variations in forces in the chain. It can be noted that this has in particular the effect of limiting mechanical fatigue in the chain, and therefore of increasing its service life.

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

Thus, it is conceivable to replace the barrel 32 by another subset having the same driving function. Such a subassembly comprises for example a beam spring operating in flexion, and to which the pulley 38 is coupled by means of one or more connecting pieces transforming the flexing movement of the beam spring into a rotation movement of the pulley 38. The function of such a beam spring is the same as that of the barrel spring 35: urge, via the pulley 38 and the chain 40, the part 10 of the hours towards its rest position.

claims

Claims (6)

1. Repeating mechanism (5) for a striking timepiece (1), which includes: - a snail (6) for hours, - an hour piece (10) carrying an hour feeler (11) and mounted in rotation about an axis (A1) of the hours between: a rest position in which the hour feeler (11) is angularly moved away from the hour snail (6), a reading position in which the hour feeler (11) comes into contact with the hour snail (7), - an hour spring (19), which recalls the hour piece (10) towards its reading position, - a pulley (38) rotatably mounted about a pulley axis (A4), - A chain (40) capable of being partially wound 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 part (10) of the hours, - a return spring (35) coupled to the pulley (38), and by which the latter urges, via the chain (40), the part (10) for hours towards its rest position, characterized in that the pulley (38) defines a peripheral cam path (39) which extends in a spiral around the pulley axis (A4). 2. Mechanism (5) according to claim 1, in which the pulley (38) and the chain (40) jointly define, on the cam path (39), a point (M) of contact whose distance (L) to the barrel axis (A4) decreases with the winding of the chain (38). CH 714 504 A2 3. Mechanism (5) according to claim 1 or claim 2, wherein the variation of the distance (L) to the axis (A4) of pulley according to the winding of the chain (38) is linear. 4. 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) of barrel varies in a proportion between 5% and 20% 5. Repeat mechanism (5) according to one of the preceding claims, which comprises: - a striking barrel (32) including: - a barrel shaft (33) which defines an axis (A4) of the barrel coincident with the axis (A4) of the pulley, - a barrel drum (34), a barrel spring (35), one internal end (36) of which is integral with the barrel shaft (33) and one external end (37) of which is integral with the barrel drum (34), and - The pulley (38), coupled in rotation to the barrel spring (35). 6. Timepiece (1), such as a watch, equipped with a repeating mechanism (5) according to one of the preceding claims.