EP2718769A2

EP2718769A2 - Source of mechanical energy for a clock movement with preset output torque

Info

Publication number: EP2718769A2
Application number: EP12732989.4A
Authority: EP
Inventors: Pascal Winkler
Original assignee: Haute Ecole Arc
Current assignee: Haute Ecole Arc
Priority date: 2011-06-10
Filing date: 2012-06-08
Publication date: 2014-04-16
Anticipated expiration: 2032-06-08
Also published as: WO2012168443A2; WO2012168443A3; EP2718769B1; CH705079A1

Abstract

The present invention relates to a mechanism designed to deliver mechanical energy to a finishing gear train of a clock movement in the form of a predefined output torque transmitted to a first mobile (20, 120) of the finishing gear train. The mechanism comprises a barrel (1) mainspring (3), one end of which is secured to a shaft (5, 105) and the other end of which is secured to a drum (2, 102), one of these being intended to be connected kinematically to the finishing gear train, and a set of gears designed to provide a kinematic connection between the ends of the spring and allow the transfer of mechanical energy between them. The set of gears comprises a planetary gear set (24, 26, 28, 30, 32, 34, 102, 126, 128, 130, 132, 134) having a first input - output (24, 134) intended to be connected to a winding mechanism (7) that resets said main spring (3), a second input - output (34, 102) connected to one end of the main spring and a third input - output (30, 130) connected to the other end of the main spring. In addition, the planetary gear set comprises a planet gear (26, 126) comprising a first non-circular gear wheel (28, 128) set in mesh with a first non-circular sun gear (30, 130).

Description

SOURCE OF MECHANICAL ENERGY FOR WATCHMAKING MOVEMENT

A PREDEFINED OUTPUT COUPLE

Technical area

The present invention relates to a mechanism, arranged to deliver mechanical energy to a finishing gear of a watch movement in the form of a predefined output torque transmitted to a first mobile of the work train. This mechanism comprises a barrel spring whose one end, internal, is secured to a barrel shaft and an outer end is secured to a barrel drum, a first of these ends being intended to be kinematically connected to the first mobile the finishing gear. The mechanism further comprises a gear train arranged to provide a kinematic connection between the ends of the mainspring and allow a transfer of mechanical energy between them.

State of the art

The realization of mechanical energy sources for watch movements is complex and requires the simultaneous consideration of several issues more or less related to each other.

Such a source of mechanical energy must have a limited footprint but, at the same time, it must be able to store enough mechanical energy to provide a satisfactory power reserve to the corresponding watch movement. Note that the amount of energy that can be stored in a barrel is directly proportional to the volume of the barrel.

[0004] A main disadvantage of the barrel springs resides in the fact that the output torque delivered by the corresponding barrel is not stable as a function of the state of charge of the spring, that is to say at all. along the winding of the barrel. The barrel spring being intended to supply a mechanical resonator with mechanical energy, to maintain the oscillations by means of a finishing train, a fluctuation of the torque that it delivers causes a fluctuation of the period of the oscillations of the mechanical resonator, an undesirable variation of the accuracy of the watch movement.

It follows from the above that, in general, a range of use of the mainspring is defined, in which the torque variation between the highest and the lowest load states of the range is judged satisfactory. This implies that a portion of the energy stored by the mainspring can not be exploited.

Various complex mechanisms have been proposed in the prior art to stabilize the torque delivered to the mechanical oscillator, including constant force escapements or equal winding.

However, the construction of these mechanisms, arranged downstream of the source of mechanical energy, is delicate and limits the implementation to models of timepieces of very high-end.

Some solutions have been proposed to act more upstream, directly at the source of mechanical energy.

An example of such a mechanism, intended in particular to reduce the amplitude of the variation of the torque delivered to the work train, is described in the patent application EP 2042944 A1. This document describes a watch movement whose mechanical energy source is made in the form of a barrel housing a spring, in a conventional manner. The movement also comprises a mechanism for counting the power reserve making it possible to know at each moment the state of charge of the mainspring.

This counting mechanism controls a switch arranged to control the movements of a rocker for acting on a clutch. The clutch is disposed in a gear train providing a kinematic connection between the barrel drum and the barrel shaft, to allow a transfer of mechanical energy between the two ends of the mainspring, more specifically, a reinjection of the energy delivered by the drum in the mainspring through the barrel shaft. Depending on the angular position of the rocker, the clutch is either in an engaged configuration, in which a transfer mechanical energy is possible, either in a disengaged configuration, in which the transfer of mechanical energy is not possible.

Thus, starting from a high load state of the mainspring, the clutch is in its engaged configuration and a portion of the mechanical energy delivered by the drum is transferred from the outer end of the mainspring to its inner end, through the gear train. When the counting mechanism detects that the state of charge of the spring reaches a predefined low value, it is necessary to flip the scale to move the clutch into its disengaged configuration, thereby interrupting the energy transfer. From this moment, all the energy delivered by the drum is sent into the finishing gear of the watch movement.

[001 1] Thanks to this mechanism, the maximum amplitude of variation of the torque delivered by the barrel drum is lower than with a conventional mechanical energy source, in particular because it makes it possible to limit the initial value of the torque delivered when the mainspring is fully loaded.

[0012] Two additional advantages are furthermore obtained. On the one hand, the maximum torque delivered being lower than that of the energy sources of the prior art, the wear of the finishing gear train is reduced. On the other hand, the fact of reloading the mainspring with its excess energy, at the beginning of unwinding, makes it possible to increase the power reserve of the corresponding clock movement.

However, the mechanism described above only partially meets the problem presented above in relation to the variation of the torque delivered by the barrel. It will be noted in particular that, from the moment when the clutch is placed in its disengaged configuration, the described energy source starts operating in the same manner as a conventional energy source, that is to say ie by presenting the same progressive decay of the delivered torque. This gives two operating ranges associated with similar torque variations but respective smaller amplitudes compared to the prior art. It will also be noted that the structure of this mechanism is complex and cumbersome, not only from the point of view of the structure of the counting mechanism of the power reserve, which has arrangements in relation to the state of the art, but also in the implementation of the gear train ensuring the reinjection of mechanical energy to the barrel shaft.

Disclosure of the invention

A main object of the present invention is to provide a simple structural mechanism, compact and acting directly at the source of mechanical energy, to limit as much as possible the variation of the torque delivered.

For this purpose, the present invention relates more particularly to a mechanism of the type mentioned above, characterized in that the gear train comprises a planetary gear having

a first input-output intended to be kinematically connected to a winding mechanism of the mainspring,

a second input-output kinematically connected to one end of the mainspring, and

a third input-output kinematically connected to the other end of the mainspring.

Such a construction simplifies the mechanism compared to that which has just been described in connection with the prior art, providing a permanent kinematic connection between the two ends of the mainspring, thanks to the implementation of a planetary gear.

In addition, the planetary gear comprises a satellite comprising a first non-circular wheel arranged in engagement with a first non-circular sun gear. The amount of energy reinjected from one end of the mainspring to the other can be controlled. In particular, the non-circular wheels may have respective peripheries such that the torque transmitted to the first mobile of the work train is substantially constant.

According to a first embodiment, it is advantageous to provide that the output torque is transmitted to the gear train from barrel drum, the planetary gear being arranged to allow energy transfer from the outer end of the mainspring to its inner end.

In this case, the planetary gear preferably comprises a satellite carrier, intended to be kinematically connected to the winding mechanism and carrying the satellite whose first non-circular wheel is secured to a second satellite wheel and coaxial to this last, the first non-circular satellite wheel having a kinematic connection with the barrel drum, while the first non-circular sun wheel has a kinematic connection with the barrel shaft. In addition, the first non-circular solar wheel is advantageously coaxial with the barrel shaft being integral with the latter in rotation.

Thanks to these characteristics, few modifications are necessary, starting from a conventional barrel, to implement the mechanism according to the invention. The mechanism having the above characteristics makes it possible to reinject a portion of the energy delivered by the barrel drum at its shaft. Thanks to the non-circular shape of the wheels of the planetary gear, the portion of energy taken out of the drum to be reinjected can be adjusted continuously, depending on the state of charge of the mainspring and therefore, depending on the torque delivered to the finishing gear. It is thus possible to take at each moment a quantity of mechanical energy such that the torque actually delivered to the work train is substantially constant.

In the case above, the mechanism preferably comprises a second sun gear rotationally integral with the barrel drum and arranged in engagement with the second satellite wheel.

According to an alternative embodiment, the sun gear may further be arranged to allow energy transfer from the inner end of the mainspring to its outer end or the finishing gear.

In this case, the drum drum advantageously defines a planet carrier of the planetary gear, the latter bearing the satellite of which the first non-circular wheel is secured to a second non-circular and coaxial satellite wheel to the latter. The first non-circular satellite wheel then has a kinematic connection with the barrel shaft, via the first non-circular sun wheel, the second non-circular satellite wheel being intended to have a kinematic connection with the winding mechanism. by means of a second non-circular solar wheel.

The second non-circular sun wheel is preferably coaxial with the barrel shaft being free to rotate relative thereto.

With these characteristics, we obtain an additional effect with reference to the first embodiment described above, because the energy can not only be fed back to the barrel shaft when the output torque delivered by the drum is greater than the needs, but can also be taken from the barrel shaft when the output torque delivered by the barrel drum becomes insufficient.

The present invention also relates to a watch movement provided with such a mechanism and a timepiece comprising such a watch movement.

Brief description of the drawings

Other features and advantages of the present invention will appear more clearly on reading the detailed description of preferred embodiments which follows, made with reference to the accompanying drawings given by way of non-limiting examples and in which:

[0029] - Figures 1a, 1b and 1c show diagrammatic diagrams illustrating the operation of a mechanism according to a first preferred embodiment of the present invention;

[0030] FIGS. 2a and 2b show views, respectively from above and in cross section, of the mechanism of FIGS. 1a to 1c;

[0031] FIG. 3 represents a diagram illustrating the result of calculations carried out for the implementation of the mechanism of FIGS. 2a and 2b;

[0032] FIG. 4 represents a comparative diagram illustrating the effects of the mechanism of FIGS. 2a and 2b with reference to other constructions; [0033] - Figure 5 shows a diagram illustrating the behavior of the mechanism of Figures 2a and 2b;

[0034] FIGS. 6a, 6b and 6c show schematic diagrams illustrating the operation of a mechanism according to a second preferred embodiment of the present invention;

[0035] FIGS. 7a and 7b show views, respectively from above and in cross section, of the mechanism of FIGS. 6a to 6c;

[0036] FIG. 8 represents a diagram illustrating the result of calculations carried out for the implementation of the mechanism of FIGS. 7a and 7b;

FIG. 9 represents a comparative diagram illustrating the effects of the mechanism of FIGS. 7a and 7b with reference to other constructions, and

[0038] - Figure 10 shows a diagram illustrating the behavior of the mechanism of Figures 7a and 7b.

Mode (s) of realization of the invention

A basic principle of the present invention lies in the implementation of a planetary gear train in a gear train defining a kinematic connection between the two ends of a mainspring, for reinjecting mechanical energy. taken from one to the other.

In the embodiments that will be described in connection with the figures, by way of nonlimiting illustration, a mainspring delivers energy to a finishing gear train via a barrel drum and is reloaded by the shaft of the barrel, while the planetary gear is of the type with two solar wheels and double satellite, and comprises at least two wheels whose periphery is non-circular. Two preferred embodiments meeting these characteristics will be described, it being understood that one skilled in the art can adapt the teaching of this text according to his own needs, without departing from the scope of the present invention. For example, it is possible to implement constructions in which the spring is recharged by the drum and connected to the work train by the barrel shaft.

Figures 1a, 1b and 1c show diagrammatic diagrams illustrating the operation of a mechanism according to a first embodiment of the invention. preferred embodiment of the present invention. According to this first embodiment, the reinjection of the mechanical energy occurs only unidirectionally, that is to say always from one end of the mainspring to the other.

A planetary gear generally comprises three inputs / outputs which have been referenced by A, B and C in FIGS. 1a to 1c, C being a satellite carrier, while the D block schematizes the satellite of the planetary gear. .

The mechanism according to the present invention comprises a barrel 1 comprising a drum 2 housing a barrel spring 3, whose outer end is integral with the drum and the inner end is integral with a bung 4, itself integral of a barrel tree 5.

The barrel 1 is intended to be associated with a watch movement to maintain the oscillations of a mechanical resonator 6, schematized here by a sprung-balance (whose spiral is not shown) cooperating with an escapement. The transmission of mechanical energy from the barrel drum 2 to the resonator is performed by a gear train not shown here.

The watch movement conventionnellennent includes a winding mechanism of the spring 3 barrel, schematized here by a winding rod 7.

As will be apparent from Figures 2a and 2b, A and C here represent inputs of the planetary gear, while B represents an output of the planetary gear. More specifically, the inlet A has a kinematic connection with the barrel drum 2, the inlet C with the winding mechanism, and the outlet B with the barrel shaft 5.

Figure 1 illustrates the situation corresponding to the winding of the mainspring from the winding mechanism.

In this case, it can be considered that during winding, the barrel drum is fixed, so that A is fixed, which is schematized by discontinuous lines. The actuation of the winding mechanism causes a rotation of the planet carrier C and at the same time of B, via the satellite D, which has the effect of recharging the mainspring 3, in a manner similar to a conventional mechanism . FIG. 1b illustrates the situation corresponding to the current operation of the watch movement, that is to say when the drum unwinds to maintain the oscillations of the resonator 6. More precisely, FIG. 1b corresponds to the case where the 3 barrel spring is heavily loaded.

In this case, the carrier is immobilized, for example by a pawl provided in the winding mechanism, while the barrel drum 2 rotates to transmit mechanical energy to the gear train. The rotation of the drum causes that of A which causes that of B via the satellite D. Thus, as shown schematically in Figure 1b, a portion of the mechanical energy delivered by the barrel drum is reinjected at the level of barrel shaft for reloading the barrel spring 3.

FIG. 1 c also illustrates a situation corresponding to the current operation of the watch movement, that is to say when the drum unwinds to maintain the oscillations of the resonator 6. More precisely, FIG. 1c corresponds to the case where the barrel spring 3 is weakly loaded.

In this case, it appears from Figure 1 c that the amount of energy reinjected into the barrel by its shaft is reduced compared to the situation of Figure 1b. When the barrel is further unwound, without being reassembled, the transfer of mechanical energy from the drum to the shaft can be greatly reduced to allow the oscillations of the resonator 6 to continue.

Figures 2a and 2b show views, respectively from above and in cross section along line II-II of Figure 2a, of a mechanism having the characteristics which have just been described in connection with Figures 1a. at 1 tbsp.

The first movable wheel of the issage end, here a mobile medium 20, has been shown for illustrative purposes in Figures 2a and 2b, the latter comprising a pinion 21, arranged in engagement with the drum 2 of barrel, and a wheel 22, for transmitting the mechanical energy received from the barrel to the rest of the work train.

The planetary gear is arranged on the drum 2 and comprises a ratchet 24 (shown partially broken away in FIG. 2a for more clarity) playing the role of the planet carrier C, free to rotate with reference to the bung 4. The ratchet carries a satellite 26 comprising a first non-circular wheel 28 arranged in engagement with a first non-circular solar wheel 30, the latter being coaxial to the barrel shaft 5 and secured to the latter.

The satellite further carries a second wheel 32, circular and arranged in engagement with a second sun gear 34, also circular. The wheels 28 and 32 are integral with each other in rotation.

This construction emerges more clearly from Figure 2b, on which it appears that the second sun gear here has the shape of a pinion, the latter being integral in rotation with the barrel drum 2. The pinion can for example be driven into the drum.

The operation of this mechanism is as described above, in connection with Figures 1a to 1c.

The proportion of the mechanical energy delivered by the drum 2 which is fed back to the plug 4 can be adjusted according to the peripheries of the non-circular wheels 28, 30. In particular, these peripheries can advantageously be chosen in such a way that the torque actually delivered by the drum to the work train is constant regardless of the state of charge of the mainspring.

Indeed, it is possible to define a system of differential equations governing the operation of the mechanism that has just been described.

The moment of the barrel (Mbariiiet) depends on the angle of the drum (ΘΑ) and the angle of the plug (ΘΒ). It can be described by a continuous function f (0 _A , Θ _Β ):

M _bariUet = f (e _A , e _B )

For example, this function could be:

Where M _armed is the moment when the barrel is fully armed and k is the spring constant (rigidity).

At equilibrium, the sum of the forces acting on the satellite is zero: Where p _x , is the pitch radius of the mobile x, at the point of contact.

At any time of operation, the different gears must roll without sliding on each other. This translates into identical circumferential speeds:

This last equation can also be written in the differential form:

At any time of operation, the different gear wheels must remain in contact two by two on their line of centers. This translates into the fact that the sum of the primitive rays is equal to the center distance (e):

[0075] and

P _B + p _SB = e

In these equations, PA is the radius of pinion 34, PB that of wheel 30, PSA that of wheel 32, and PSB that of wheel 28.

The equations above constitute a system of differential equations.

The resolution of this system of equations makes it possible to obtain the (primitive) shapes that the gears must have to obtain the Mrouage pair from a cylinder having a torque Mbariiiet = Î (0A, ΘΒ).

The existence of an analytical solution depends on the function Mbariiiet = Î (0A, ΘΒ). On the other hand, it is necessary to introduce some additional conditions on the geometry of the gears to restrict the solutions to feasible shapes.

Indeed, it is possible to consider different alternative or cumulative special conditions to solve the system of equations above:

a) it is desired, according to a preferred embodiment, that the moment available for the gear (Mrouage) is constant;

b) by virtue of the principle of conservation of the energy, it is possible to impose that the value of Mrouage is equal to the energy stored in the cylinder divided by the total angle of rotation of the drum. Indeed, the energy is worth E = f Md9;

(c) the center distance can be set;

d) we can impose that Mbariiiet = Marmé - Ι <(ΘΑ-ΘΒ) if ΘΑ> ΘΒ and 0 otherwise. We can fix Marmé. The number of turns of development of the spring in the barrel can be fixed;

e) it is preferable to use one-turn circular gears, i.e., the primitive is in a xy plane. In other words, the corresponding wheel can be cut in a flat plate, as opposed to non-circular gears with several turns whose contact line rises in the direction of the z-axis (shaped snail shell);

f) it can be imposed that the pinion 34 is circular;

g) it is required that the radius of the wheel 30 is less than the center distance; h) it is possible to impose a minimum value of the gear ratio between the wheel 28 of the satellite and the wheel 30 integral with the bung. This allows to save space in the center of the wheel 30 to have a hub.

By introducing all the conditions set out above in the system of equations explained above, we can solve the equations and obtain primitives for the different gears of the planetary gear.

These primitives are illustrated in a nonlimiting manner in Figure 3. The determination of these primitives then allows the realization of the wheels as shown in Figures 2a and 2b.

FIG. 4 represents a comparative diagram illustrating the effects of the mechanism of FIGS. 2a and 2b with reference to other constructions, by illustrating the available torque as a function of the angular position of the barrel drum.

The conventional M-wheel curve represents the characteristic of the barrel without the reinjection mechanism according to the present invention.

The curve M with reinjection represents the torque available to the end gear issage as a function of the angular position of the drum for the particular case calculated previously. It can be seen that the available torque at finishing gear is quite constant. On the other hand, it also shows that the area under the curve, which represents the mechanical energy, is equivalent to that under the curve M _r0 conventional creep.

[0085] The curve M _re ssort with reinjection shows that, thanks to the mechanism of the present invention, the barrel spring discharges slowly at the beginning of the discharge (when the torque is high) and faster when disarmed.

It should also be noted that, as the drum rotates at a constant speed, the abscissa of FIG. 4 represents proportionally the time that passes when the watch movement is a current operating mode.

Finally, the MEDT curve schematically illustrates the evolution of the torque available to the gear train with the implementation of the mechanism mentioned above in relation to the prior art (EP 2042944 A1).

FIG. 5 represents a diagram illustrating the angular position of the bung with respect to the angular position of the barrel drum, during the discharge time of the mainspring (the time being proportional to Otambour).

It can be seen in FIG. 5 that at the beginning of discharge of the mainspring, the speed of the bung (slope of the curve) is maximum and that this speed tends to cancel when the cylinder is unloaded. This behavior is explained by the fact that the power reinjected to the bung is important when the spring is strongly armed and almost zero when the spring is disarmed.

Figures 6a, 6b and 6c show schematic diagrams illustrating the operation of a mechanism according to a second preferred embodiment of the present invention. According to this second embodiment, the reinjection of the mechanical energy is likely to occur bidirectionally, that is to say from one end of the mainspring to the other and vice versa.

The same reference signs as in Figures 1a to 1c have been maintained in Figures 6a to 6c, to simplify understanding. Thus, the planetary gear can advantageously comprise three inputs / outputs, as in the first embodiment, which have been referenced by A, B and C in FIGS. 6a to 6c, C being a satellite carrier, while block D schematizes the satellite of the planetary gear.

As will be apparent from Figures 7a and 7b, A here represents an input of the planetary gear, while B and C represent inputs-outputs of the planetary gear. More specifically, the input A has a kinematic connection with the winding mechanism, while the inputs-outputs B and C have respective kinematic links with the barrel shaft 5 and with the barrel drum 2.

Figure 6a illustrates the situation corresponding to the winding of the mainspring from the winding mechanism.

In this case, it can be considered that during winding, the barrel drum is fixed, so that C is fixed, which is schematized by discontinuous lines. The actuation of the winding mechanism causes a rotation of the satellite D and at the same time B, which has the effect of reloading the barrel spring 3, similarly to a conventional mechanism.

6b illustrates the situation corresponding to the current operation of the watch movement, that is to say when the barrel is unwound to maintain the oscillations of the resonator 6. More specifically, Figure 6b corresponds to the case where the spring 3 barrel is heavily loaded.

In this case, A is immobilized, for example by a pawl provided in the winding mechanism, while the barrel drum 2 rotates to transmit mechanical energy to the gear train. The rotation of the drum causes that of C which causes that of B, via the satellite D. Thus, as shown schematically in Figure 6b, a portion of the mechanical energy delivered by the drum drum is reinjected at the level of barrel shaft for reloading the barrel spring 3.

Figure 6c also illustrates a situation corresponding to the current operation of the watch movement, that is to say when the barrel unwinds to maintain oscillations of the resonator 6. More precisely, FIG. 6c corresponds to the case where the barrel spring 3 is weakly loaded.

In this case, it appears from Figure 6c that mechanical energy can be taken by B at the barrel shaft to be reinjected into the gear train, through the carrier C .

Figures 7a and 7b show views, respectively from above and in cross section along the line VII-VII of Figure 7a, of a mechanism having the characteristics which have just been described in relation to Figures 6a to 6c.

[00101] A first movable wheel end issage, here a mobile of high average 120, has been shown for illustrative purposes in Figures 7a and 7b, it comprising a pinion 121, arranged in engagement with the drum 102 of barrel, and a wheel 122, for transmitting mechanical energy received from the barrel to the rest of the work train.

The planetary gear is arranged on the drum 102 and comprises a ratchet 124 (shown partially broken away in FIG. 7a for the sake of clarity) mounted free to rotate on the barrel shaft 105. In particular, it can be seen from FIG. FIG. 7b shows that the barrel drum 102 plays the role of the planet carrier C, free to rotate with reference to the bung 104. The drum 102 carries a satellite 126 comprising a first non-circular wheel

128 arranged in engagement with a first non-circular solar wheel 130, the latter being coaxial with the barrel shaft 105 and secured thereto.

The satellite further carries a second non-circular wheel 132 and arranged in engagement with a second non-circular sun wheel 134. The latter is intended to have a kinematic connection with the winding mechanism. For this purpose, it is arranged integral in rotation with the ratchet 124 intended to be rotated by the winding mechanism. The wheels 128 and 132 are integral in rotation.

The satellite-carrier configuration is more clearly apparent from FIG. 7b, in which it appears that the satellite is assembled with the barrel drum 102 by a shaft 136. The operation of this mechanism is as described above, in connection with Figures 6a to 6c.

The proportion of the mechanical energy delivered by the drum 102 which is reinjected to the plug 104 and the proportion of energy taken from the plug to be reinjected into the work train can be adjusted according to the peripheries of the wheels. In particular, these peripheries may advantageously be chosen in such a way that the torque actually delivered by the drum to the work train is constant regardless of the state of charge of the mainspring.

[00107] Indeed, it is possible to define another system of differential equations governing the operation of the mechanism according to the second preferred embodiment of the invention.

[00108] The moment of the barrel {M _bariUet ) depends on the angle of the drum (6 _C ) and the angle of the bung (Θ _Β ). I l can be described by u no continuous function f (0 _c , e _B ):

[00109] M _bariUet = f (e _c , e _B )

[001 10] For example, this function could be:

[001 1 1] where M _armed is the moment when the barrel is fully armed and k is the spring constant (rigidity).

[001 12] At equilibrium, the sum of the forces acting on the satellite is zero:

[001 13] {M _bariUet - _cog M) = M _bariUet (1 -

[001 14] where p _x , is the pitch radius of the mobile x, at the point of contact.

[001 15] At any time of operation, the different gears must roll without sliding on each other. This results in identical circumferential speeds:

[001 16] Θ _Β p _B p _SA + e _c (p _A p _SB - p _B p _SA ) = 0

[001 17] This last equation can also be written in the differential form:

[001 18] άθ _Β p _B p _SA + d0 _c (p _A p _SB - _{Pb Psa} ) = 0 At any time of operation, the different gears must stay in contact two by two on their line of centers. This translates into the fact that the sum of the primitive rays is equal to the center distance (e):

[00121] And

[00122] P _B + P _SB = e

In these equations, PA is the radius of the wheel 134, PB that of the wheel 130, PSA that of the wheel 132, and PSB that of the wheel 128.

The equations above constitute a system of differential equations.

The resolution of this system of equations makes it possible to obtain the (primitive) shapes that the gears must have to obtain the Mrouage pair from a cylinder having a pair Mbariiiet = f (0c, ΘΒ). The existence of an analytical solution depends on the function Mbariiiet = ί (θο, θβ). On the other hand, it is necessary to introduce some additional conditions on the geometry of the gears to restrict the solutions to feasible shapes.

[00125] It is possible to consider different alternative or cumulative special conditions to solve the system of equations above:

(b) by virtue of the principle of conservation of energy, it may be imposed that the value of Mrouage be equal to the mean of the moment of the barrel; (c) the center distance can be set;

d) we can impose that Mbariiiet = Marmé- Ι <(ΘΟ-ΘΒ) if 0c> ΘΒ and 0 otherwise. We can fix Marme;

e) it is preferable to use circular gears in one turn;

f) it can be imposed that the wheel 134 is identical to the wheel 128;

g) it can be imposed that the bung is found in its initial position (fully armed spring) when the drum is at the end of its race (spring completely disarmed);

(h) a minimum gear ratio may be imposed between the wheel 128 of the satellite and the wheel 130 secured to the bung. This allows to save space in the center of the wheel 130 to have a hub.

By introducing all the conditions set out above in the system of equations explained above, it is possible to solve the equations and obtain primitive values for the different gears of the planetary gear.

These primitives are illustrated in a nonlimiting manner in Figure 8. The determination of these primitives then allows the realization of the wheels as shown in Figures 7a and 7b.

FIG. 9 represents a comparative diagram illustrating the effects of the mechanism of FIGS. 7a and 7b with reference to other constructions, by illustrating the available torque as a function of the angular position of the barrel drum.

The curve M conventional wheel represents the characteristic of the barrel without the feedback mechanism according to the present invention.

The curve M gear with feedback represents the torque available to the work train according to the angular position of the drum for the particular case calculated above. It can be seen that the torque available to the finishing gear is quite constant. On the other hand, it also shows that the area under the curve, which represents the mechanical energy, is equivalent to that under the curve M _r0 conventional creep.

The curve M spring with feedback shows that, thanks to the mechanism according to the present invention, the mainspring slowly discharges at the beginning of its discharge (when its torque is high) and more quickly when it is disarmed.

It should also be noted that, as the drum rotates at a constant speed, the abscissa of Figure 9 represents proportionally the time that passes when the watch movement is a current mode of operation.

[00133] FIG. 10 represents a diagram, similar to that of FIG. 5, illustrating the angular position of the bung with respect to the position angular of the barrel drum, during the discharge time of the mainspring (the time being proportional to Otambour).

[00134] It can be seen in FIG. 10 that at the beginning of the discharge of the mainspring, the speed of the bung is maximum and that this speed vanishes when Mbariiiet = M _ro uage. The direction of rotation of the bung is reversed when the barrel is unloaded (Mbariiiet <Mrouage), so as to inject power into the train by the bung. This behavior is explained by the fact that the reinjected power to the bung is positive and important when the spring is strongly armed and negative (withdrawal) when the spring is disarmed. Unlike the unidirectional feedback mechanism, according to the first embodiment, the direction of rotation of the plug can be reversed in the present bidirectional feedback mechanism.

The foregoing description attempts to describe particular embodiments by way of non-limiting illustration and, the invention is not limited to the implementation of certain particular features which have just been described, as for example the forms specifically illustrated and described for the teeth of the various wheels, in particular the fact that they are of internal type or external type. Indeed, it is possible to replace the sun wheels by internally toothed crowns without departing from the scope of the present invention.

The skilled person will not encounter any particular difficulty to adapt the content of the present disclosure to his own needs and implement a mechanism for regulating the torque delivered to the finishing gear only partially responding to the characteristics that come from be presented without departing from the scope of the present invention.

By way of example, it is possible to provide that the non-circular wheels used traverse more than one turn on themselves without departing from the scope of the invention. In this case, these wheels would not be flat, as mentioned above.

It will be noted that, in the case of a mechanism operating with a single turn of development of the mainspring, the shape and the material of the latter can be optimized so as to restore a maximum of energy on this single development tour since the torque available to the finishing gear is controlled.

Of course, the profiles of the teeth used will be advantageously optimized to reduce the air pressures involved, while usually they are rather optimized to ensure a homogeneous transmission of torque and speed.

[00140] Advantageously, we can provide a stop mechanism of the winding when the mainspring is fully loaded. Such a stop mechanism may for example be made directly by a choice of adapted shapes of the peripheries of the non-circular wheels, each of which may have a side intended to cooperate with the side of the other wheel to define a stop.

Similarly, a disengagement device of the automatic winding mechanism could be advantageously provided to limit the stresses applied to the mechanism when the spring is fully loaded, or a device for locking the oscillating mass.

Moreover, it will be noted that several mechanisms according to the present invention can be mounted in series in a watch movement, thereby increasing the power reserve without having a torque available to the finishing gear too important.

Claims

Mechanism arranged to deliver mechanical energy to a finishing gear of a watch movement in the form of a predefined output torque transmitted to a first mobile (20, 120) of the work train, the mechanism comprising

a spring (3) of barrel (1) whose one end, internal, is integral with a barrel shaft (5, 105) and an outer end, is integral with a drum (2, 102) barrel, a first of said ends being intended to be kinematically connected to the first mobile of the work train,

a gear train arranged to provide a kinematic connection between said ends of said mainspring and to allow a transfer of mechanical energy between them,

characterized in that said gear train comprises a sun gear (24, 26, 28, 30, 32, 34, 102, 126, 128, 130, 132, 134) having a first input-output (24, 1 34) intended to be connected kinematically to a winding mechanism (7) of said mainspring (3),

a second input-output (34, 102) kinematically connected to an end of said mainspring, and

a third input-output (30, 130) kinematically connected to the other end of said mainspring, and

in that said sun gear (24, 26, 28, 30, 32, 34, 102, 126, 128, 130, 132, 134) comprises a satellite (26, 126) including a first non-circular wheel (28, 128) arranged in engagement with a first non-circular sun wheel (30, 130).

Mechanism according to claim 1, characterized in that said non-circular wheels (28, 30, 128, 130) have respective peripheries such that the torque transmitted to the first mobile (20, 120) of the work train is substantially constant.

Mechanism according to claim 1 or 2, characterized in that said output torque is transmitted to the work train from said drum (2, 102) of barrel (1), said planetary gear (24, 26, 28, 30, 32 , 34, 102, 126, 128, 130, 132, 134) being arranged to allow energy transfer from said outer end of said barrel spring (3) to said inner end.

4. Mechanism according to revendication 3, characterized in that it it planetary gear (24, 26, 28, 30, 32, 34) comprises a carrier-satellite (24), intended to be kinematically connected to the winding mechanism (7). ) and, carrying said satellite (26) of which said first non-circular wheel (28) is integral with and coaxial with a second satellite wheel (32), said first non-circular satellite wheel (28) having a connection kinematic with said barrel drum (2), said first non-circular sun gear (30) having a kinematic connection with said barrel shaft (5).

5. Mechanism according to claim 4, characterized in that said first non-circular sun wheel (30) is coaxial with said shaft (5) barrel being integral with the latter in rotation.

6. Mechanism according to claim 4 or 5, characterized in that it comprises a second sun gear (34) integral in rotation with said barrel drum (2) and arranged in engagement with said second satellite wheel (32).

7. Mechanism according to claim 3, characterized in that said planetary gear (102, 126, 128, 130, 132, 134) is further arranged to allow a transfer of energy from said inner end of said spring (3) barrel towards said outer end or the work train.

8. Mechanism according to claim 7, characterized in that said barrel drum (102) defines a planet carrier of said planetary gear, the latter bearing said satellite (126) of which said first non-circular wheel (128) is integral with a second non-circular satellite wheel (132) coaxial with the latter, said first non-circular satellite wheel (128) having a kinematic connection with said barrel shaft (105) through said first non-circular sun gear (130), said second non-circular satellite wheel (132) being intended to have a kinematic connection with the winding mechanism (7), via a second non-circular sun wheel (134).

9. Mechanism according to claim 8, characterized in that said second noncircular sun wheel (134) is coaxial with said shaft (105) of the barrel being free to rotate relative thereto.

10. Watch movement comprising a mechanism according to any one of the preceding claims.

1 1. Timepiece comprising a watch movement according to claim 10.