EP2718769B1 - Source of mechanical energy for a clock movement with preset output torque - Google Patents

Description

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, interned, 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.

• une première entrée-sortie destinée à être reliée cinématiquement à un mécanisme de remontage du ressort de barillet,
• une seconde entrée-sortie reliée cinématiquement à une extrémité du ressort de barillet, et
• une troisième entrée-sortie reliée cinématiquement à l'autre extrémité du ressort de barillet.

The gear train advantageously 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.

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.

A main disadvantage of the barrel springs lies 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 throughout the unwinding of the spring. barrel. The mainspring is intended to feed a mechanical resonator mechanical energy, to maintain the oscillations through a finishing train, a fluctuation of the torque it delivers causes a fluctuation of the period of oscillations of the mechanical resonator , an undesirable variation of the running 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 in the range is considered 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 windings. However, the construction of these mechanisms, arranged downstream of the mechanical energy source, is delicate and limits the implementation to models of timepieces of very high quality.

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 intended to act on a clutch. The clutch is arranged 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 barrel spring, more specifically, a reinjection of the energy delivered by the drum into the spring of barrel through the barrel shaft. Depending on the angular position of the rocker, the clutch is either in an engaged configuration, in which a mechanical energy transfer is possible, or in a disengaged configuration, in which the transfer of mechanical energy is not possible.

Thus, starting from a high state of charge 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. , via the gear train. When the counting mechanism detects that the state of charge of the spring reaches a predefined low value, it pivots the rocker 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.

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 spring barrel is fully charged.

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 satisfies 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 energy source described begins to operate in an identical manner to that of a conventional energy source, that is to say, with 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 presents improvements 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.

The patent application EP 1975746 A1 describes an alternative mechanism to that which has just been described but whose construction is also very complex.

Disclosure of the invention

A main object of the present invention is to provide a mechanism of simple structure, 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 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.

Such a construction makes it possible to simplify the mechanism with respect to that which has just been described in relation with the prior art, by providing a permanent kinematic connection between the two ends of the mainspring, thanks to the implementation of a planetary gear.

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

In this case, the planetary gear preferably comprises a planet carrier, intended to be kinematically connected to the winding mechanism and, carrying the satellite whose first non-circular wheel is integral with a second satellite wheel and coaxial with the latter, 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 integral with the rotation of the barrel drum and arranged in engagement with the second satellite wheel.

According to an alternative embodiment, the planetary gear can also be arranged to allow energy transfer from the inner end of the mainspring to its outer end or the work train.

In this case, the drum drum advantageously defines a planet carrier of the sun gear, the latter carrying the satellite whose first non-circular wheel is integral with a second non-circular satellite wheel and coaxial with 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.

Thanks to these characteristics, an additional effect is obtained with reference to the first embodiment described above, because energy can not only be reinjected 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

• les figures 1a, 1b et 1c représentent des diagrammes schématiques illustrant le fonctionnement d'un mécanisme selon un premier mode de réalisation préféré de la présente invention;
• les figures 2a et 2b représentent des vues, respectivement de dessus et en coupe transversale, du mécanisme des figures 1a à 1c;
• la figure 3 représente un diagramme illustrant le résultat de calculs réalisés pour la mise en oeuvre du mécanisme des figures 2a et 2b;
• la figure 4 représente un diagramme comparatif illustrant les effets du mécanisme des figures 2a et 2b en référence à d'autres constructions;
• la figure 5 représente un diagramme illustrant le comportement du mécanisme des figures 2a et 2b;
• les figures 6a, 6b et 6c représentent des diagrammes schématiques illustrant le fonctionnement d'un mécanisme selon un second mode de réalisation préféré de la présente invention;
• les figures 7a et 7b représentent des vues, respectivement de dessus et en coupe transversale, du mécanisme des figures 6a à 6c;
• la figure 8 représente un diagramme illustrant le résultat de calculs réalisés pour la mise en oeuvre du mécanisme des figures 7a et 7b;
• la figure 9 représente un diagramme comparatif illustrant les effets du mécanisme des figures 7a et 7b en référence à d'autres constructions, et
• la figure 10 représente un diagramme illustrant le comportement du mécanisme des figures 7a et 7b.

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 as non-limiting examples and in which:

• the Figures 1a, 1b and 1 C are schematic diagrams illustrating the operation of a mechanism according to a first preferred embodiment of the present invention;
• the Figures 2a and 2b represent views, respectively from above and in cross-section, of the mechanism of Figures 1a to 1c ;
• the figure 3 represents a diagram illustrating the result of calculations made for the implementation of the mechanism of the Figures 2a and 2b ;
• the figure 4 represents a comparative diagram illustrating the effects of the mechanism of Figures 2a and 2b with reference to other constructions;
• the figure 5 represents a diagram illustrating the behavior of the mechanism of Figures 2a and 2b ;
• the Figures 6a, 6b and 6c are diagrammatic diagrams illustrating the operation of a mechanism according to a second preferred embodiment of the present invention;
• the figures 7a and 7b represent views, respectively from above and in cross-section, of the mechanism of Figures 6a to 6c ;
• the figure 8 represents a diagram illustrating the result of calculations made for the implementation of the mechanism of the figures 7a and 7b ;
• the figure 9 represents a comparative diagram illustrating the effects of the mechanism of figures 7a and 7b with reference to other constructions, and
• the figure 10 represents 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 the 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 drum barrel and is recharged by the cylinder. barrel shaft, 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.

The Figures 1a, 1b and 1 C are diagrammatic diagrams illustrating the operation of a mechanism according to a first 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.

In principle, a planetary gear train has three inputs / outputs which have been referenced by A, B and C on the figures 1 a at 1 c, C being a satellite carrier, while block D 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 with a barrel shaft 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 conventionally comprises a mechanism for winding the barrel spring 3, schematized here by a winding stem 7.

As will emerge 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.

The figure 1a illustrates the situation corresponding to the winding of the mainspring from the winding mechanism.

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

The figure 1b illustrates the situation corresponding to the current operation of the watch movement, that is to say when the barrel unwinds to maintain the oscillations of the resonator 6. More specifically, the figure 1 b corresponds to the case where the barrel spring 3 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 work train. The rotation of the drum causes that of A which drives that of B via the satellite D. Thus, as schematized on the figure 1b , part of the mechanical energy delivered by the barrel drum is reinjected at the barrel shaft to reload the barrel spring 3.

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

In this case, it appears from figure 1c that the amount of energy reinjected into the barrel by its shaft is reduced compared to the situation of the 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.

The Figures 2a and 2b represent views, respectively from above and in cross-section along the line II-II of the figure 2a , of a mechanism having the characteristics which have just been described in relation to the figures 1 a to 1 c.

A first mobile of the work train, here a mobile of high average 20, has been represented for illustrative purposes on Figures 2a and 2b , the latter comprising a pinion 21, arranged in engagement with the barrel drum 2, 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 on the figure 2a for the sake of 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, this last being coaxial with 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 the 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 functioning of this mechanism is as described above, in relation to the figures 1 a to 1 c.

The proportion of the mechanical energy delivered by the drum 2 which is fed back to the plug 4 can be adjusted as a function of the peripheries of the non-circular wheels 28, 30. In particular, these peripheries can advantageously be chosen in such a way that the torque effectively 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 just described.

The moment of the barrel (M _barrel ) depends on the angle of the drum (θ _A ) and the angle of the bung (θ _B ). It can be described by a continuous function f (θ _A , θ _B ): $$M_{\mathit{barrel}}=f\left({\theta }_{\mathrm{AT}},{\theta }_B\right)$$

For example, this function could be: $$f\left({\theta }_{\mathrm{AT}},{\theta }_B\right)=\{\begin{array}{ll}{M}_{\mathit{armed}}-k\left({\theta }_{\mathrm{AT}}-{\theta }_B\right)& \mathrm{if}{\theta }_{\mathrm{AT}}>{\theta }_{\mathrm{B}}\\ 0& \mathrm{if\; not}\end{array}$$

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

At equilibrium, the sum of the forces acting on the satellite is zero: $$\frac{{\mathit{M}}_{\mathit{barrel}}-{\mathit{M}}_{\mathit{cog}}}{{\rho }_{\mathit{AT}}}{\rho }_{\mathit{HER}}=M_{\mathit{barrel}}\frac{{\rho }_{\mathit{SB}}}{{\rho }_{\mathit{B}}}$$

where ρ _x , is the pitch radius of the mobile x, at the point of contact.

At any time during operation, the different gears must roll without sliding on each other. This results in identical circumferential speeds: $${\stackrel{°}{\theta }}_{\mathrm{AT}}\frac{{\rho }_{\mathrm{AT}}}{{\rho }_{\mathit{HER}}}={\stackrel{°}{\theta }}_B\frac{{\rho }_B}{{\rho }_{\mathit{SB}}}$$

This last equation can also be written in the differential form: $$d{\theta }_{\mathrm{AT}}\frac{{\rho }_{\mathrm{AT}}}{{\rho }_{\mathit{HER}}}=d{\theta }_B\frac{{\rho }_B}{{\rho }_{\mathit{SB}}}$$

et $${\rho }_B+{\rho }_{\mathit{SB}}=e$$

At all times of operation, the different gears 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): $${\rho }_{\mathrm{AT}}+{\rho }_{\mathit{HER}}=e$$

and $${\rho }_B+{\rho }_{\mathit{SB}}=e$$

In these equations, ρ _A is the radius of the pinion 34, ρ _B that of the wheel 30, ρ _SA that of the wheel 32, and ρ _SB that of the wheel 28.

The equations above are a system of differential equations. Solving this system of equations provides forms (primitives) that must have the gears to get the _wheel torque M from a barrel having a _barrel torque M = f (θ _A, θ _B). The existence of an analytical solution depends on the M _barrel function = f (θ _A , θ _B ). 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.

1. a) on veut, selon une réalisation préférée, que le moment disponible pour le rouage (M_rouage) soit constant;
2. b) en vertu du principe de conservation de l'énergie, on peut imposer que la valeur de M_rouage soit égale à l'énergie stockée dans le barillet divisée par l'angle total de rotation du tambour. En effet, l'énergie vaut E= ∫ Mdθ;
3. c) on peut fixer l'entraxe;
4. d) on peut imposer que M_barillet = M_armé - k(θ_A-θ_B) si θ_A > θ_B et 0 sinon. On peut fixer M_armé. On peut fixer le nombre de tours de développement du ressort dans le barillet;
5. e) on veut préférablement utiliser des engrenages circulaires à un tour, c'est-à-dire que la primitive est dans un plan xy. Autrement dit, la roue correspondante peut être découpée dans une plaque plane, par opposition à des engrenages non circulaires à plusieurs tours dont la ligne de contact s'élève selon la direction de l'axe z (en forme de coquille d'escargot);
6. f) on peut imposer que le pignon 34 est circulaire;
7. g) on impose que le rayon de la roue 30 est inférieur à l'entraxe;
8. h) on peut imposer une valeur minimale du rapport d'engrenage entre la roue 28 du satellite et la roue 30 solidaire de la bonde. Cela permet de ménager de l'espace au centre de la roue 30 pour y disposer un moyeu.

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

1. a) it is desired, according to a preferred embodiment, that the moment available for the gear train (M _wheel ) is constant;
2. b) by virtue of the principle of conservation of energy, it can be imposed that the value of M _cog 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 = ∫ Mdθ ;
3. (c) the center distance can be set;
4. d) we can impose that M _barrel = M _armed - k (θ _A -θ _B ) if θ _A > θ _B and 0 otherwise. One can fix M _armed . The number of turns of development of the spring in the barrel can be fixed;
5. 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);
6. f) it can be imposed that the pinion 34 is circular;
7. g) it is required that the radius of the wheel 30 is less than the center distance;
8. 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, the equations can be solved and primitives obtained for the different gears of the planetary gear.

These primitives are illustrated in a non-limiting way on the figure 3 . The determination of these primitives then allows the realization of the wheels as they are represented on the Figures 2a and 2b .

The figure 4 represents a comparative diagram illustrating the effects of the mechanism of Figures 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 feedback mechanism according to the present invention.

The curve M _{gear with feedback} represents the torque available to the finishing gear according to the angular position of the drum for the particular case calculated previously. It can be seen that the torque available to the finishing gear is quite constant. On the other hand, it is also noted that the area under the curve, which represents the mechanical energy, is equivalent to that located under the curve M _{conventional wheel} .

Curve M _{spring with reinjection} 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 the figure 4 proportionally represents the time that passes when the watch movement is a current mode of operation.

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

The figure 5 is a diagram illustrating the angular position of the plug relative to the angular position of the barrel drum, during the discharge time of the barrel spring (the time being proportional to θ _drum ).

We see on the figure 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.

The Figures 6a, 6b and 6c are diagrammatic 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 intervene bidirectionally, that is to say from one end of the mainspring to the other and vice versa.

The same reference signs as on the figures 1 a at 1c were kept on the 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 on the Figures 6a to 6c , C being a satellite carrier, while block D schematizes the satellite of the planetary gear.

As will emerge figures 7a and 7b A represents here 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.

The 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 rewinding, 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 of B, which has the effect of reloading the barrel spring 3, similarly to a conventional mechanism.

The figure 6b illustrates the situation corresponding to the current operation of the watch movement, that is to say when the barrel unwinds to maintain the oscillations of the resonator 6. More specifically, the figure 6b corresponds to the case where the barrel spring 3 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 work train. The rotation of the drum causes that of C which causes that of B, via the satellite D. Thus, as schematized on the figure 6b , part of the mechanical energy delivered by the barrel drum is reinjected at the barrel shaft to reload the barrel spring 3.

The 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 the oscillations of the resonator 6. More specifically, the Figure 6c corresponds to the case where the spring 3 barrel 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, via the planet carrier C.

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

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

The planetary gear is arranged on the drum 102 and includes a ratchet 124 (shown partially broken away on the figure 7a for clarity) mounted free to rotate on the barrel shaft 105. In particular, it is apparent from the figure 7b the 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 sun wheel 130 , the latter being coaxial with the barrel shaft 105 and integral with the latter.

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 the figure 7b , on which it appears that the satellite is assembled to the barrel drum 102 by a shaft 136.

The functioning of this mechanism is as described above, in relation to the Figures 6a to 6c .

The proportion of the mechanical energy delivered by the drum 102 which is fed back to the plug 104 and the proportion of energy taken from the plug to be reinjected into the finishing train can be adjusted according to the peripheries of the non-circular wheels 128, 130, 132 and 134. 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 another system of differential equations governing the operation of the mechanism according to the second preferred embodiment of the invention.

The moment of the barrel ( M _{bari / let} ) depends on the angle of the drum ( θ _C ) and the angle of the bung ( θ _B ). It can be described by a continuous function f (θ _C , θ _B ): $$M_{\mathit{barrel}}=f\left({\theta }_{\mathrm{VS}},{\theta }_B\right)$$

For example, this function could be: $$f\left({\theta }_{\mathrm{VS}},{\theta }_B\right)=\{\begin{array}{ll}{M}_{\mathit{armed}}-k\left({\theta }_{\mathrm{VS}}-{\theta }_B\right)& \mathrm{if}{\theta }_{\mathrm{VS}}>{\theta }_{\mathrm{B}}\\ 0& \mathrm{if\; not}\end{array}$$

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

At equilibrium, the sum of the forces acting on the satellite is zero: $$\left({\mathit{M}}_{\mathit{barrel}}-{\mathit{M}}_{\mathit{cog}}\right)\frac{{\rho }_{\mathit{HER}}}{{\rho }_{\mathit{AT}}+{\rho }_{\mathit{HER}}}=M_{\mathit{barrel}}\left(1-\frac{{\rho }_{\mathit{AT}}}{{\rho }_{\mathit{B}}}\right)$$

where ρ _x , is the pitch radius of the mobile x, at the point of contact.

At any time during operation, the different gears must roll without sliding on each other. This results in identical circumferential speeds: $${\stackrel{°}{\theta }}_B{\rho }_B{\rho }_{\mathit{HER}}+{\stackrel{°}{\theta }}_{\mathrm{VS}}\left({\rho }_{\mathrm{AT}}{\rho }_{\mathit{SB}}-{\rho }_B{\rho }_{\mathit{HER}}\right)=0$$

This last equation can also be written in the differential form: $$d{\theta }_B{\rho }_B{\rho }_{\mathit{HER}}+d{\theta }_{\mathrm{VS}}\left({\rho }_{\mathit{AT}}{\rho }_{\mathit{SB}}-{\rho }_B{\rho }_{\mathit{HER}}\right)=0$$

Et $${\rho }_B+{\rho }_{\mathit{SB}}=e$$

At all times of operation, the different gears 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): $${\rho }_{\mathrm{AT}}+{\rho }_{\mathit{HER}}=e$$

And $${\rho }_B+{\rho }_{\mathit{SB}}=e$$

In these equations, ρ _A is the radius of the wheel 134, ρ _B that of the wheel 130, ρ _SA that of the wheel 132, and ρ _SB that of the wheel 128.

The equations above are a system of differential equations. Solving this system of equations provides forms (primitives) that must have the gears to get the _wheel torque M from a barrel having a _barrel torque M = f (θ _C, θ _B). The existence of an analytical solution depends on the M _barrel function = f (θ _C , θ _B ). 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.

1. a) on veut, selon une réalisation préférée, que le moment disponible pour le rouage (M_rouage) soit constant;
2. b) en vertu du principe de conservation de l'énergie, on peut imposer que la valeur de M_rouage soit égale à la moyenne du moment du barillet;
3. c) on peut fixer l'entraxe;
4. d) on peut imposer que M_barillet = M_armé - k(θ_C-θ_B) si θ_C > θ_B et 0 sinon. On peut fixer M_armé;
5. e) on veut préférablement utiliser des engrenages circulaires à un tour;
6. f) on peut imposer que la roue 134 soit identique à la roue 128;
7. g) on peut imposer que la bonde se retrouve dans sa position initiale (ressort complètement armé) lorsque le tambour est à la fin de sa course (ressort complètement désarmé);
8. h) on peut imposer une valeur minimale du rapport d'engrenage entre la roue 128 du satellite et la roue 130 solidaire de la bonde. Cela permet de ménager de l'espace au centre de la roue 130 pour y disposer un moyeu.

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

1. a) it is desired, according to a preferred embodiment, that the moment available for the gear train (M _wheel ) is constant;
2. (b) by virtue of the principle of conservation of energy, it may be imposed that the value of M _cog is equal to the average of the moment of the cylinder;
3. (c) the center distance can be set;
4. d) we can impose that M _barrel = M _armed - k (θ _C -θ _B ) if θ _C > θ _B and 0 otherwise. One can fix M _armed ;
5. e) it is preferable to use circular gears in one turn;
6. f) it can be imposed that the wheel 134 is identical to the wheel 128;
7. g) we can impose that the bung is found in its initial position (fully armed spring) when the drum is at the end of its stroke (spring completely disarmed);
8. h) it is possible to impose a minimum value of the gear ratio between the wheel 128 of the satellite and the wheel 130 integral with 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, the equations can be solved and primitives obtained for the different gears of the planetary gear.

These primitives are illustrated in a non-limiting way on the figure 8 . The determination of these primitives then allows the realization of the wheels as they are represented on the figures 7a and 7b .

The figure 9 represents a comparative diagram illustrating the effects of the mechanism of figures 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 _conventional M- _wheel curve 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 finishing gear according to the angular position of the drum for the particular case calculated previously. It can be seen that the torque available to the finishing gear is quite constant. On the other hand, it is also noted that the area under the curve, which represents the mechanical energy, is equivalent to that located under the curve M _{conventional wheel} .

Curve M _{spring with reinjection} 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 the figure 9 proportionally represents the time that passes when the watch movement is a current mode of operation.

The figure 10 represents a diagram, similar to that of the figure 5 , illustrating the angular position of the bung relative to the angular position of the barrel drum, during the discharge time of the mainspring (the time being proportional to θ _drum ).

We see on the figure 10 at the beginning of discharge of the mainspring, the speed of the bung is maximum and this speed is canceled when M _cylinder = M _cog . The direction of rotation of the bung is reversed when the barrel is unloaded (M _barrel <M _wheel ), 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, 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.

Those skilled in the art will not encounter any particular difficulty in adapting the content of the present disclosure to their own needs and implementing a mechanism for regulating the torque delivered to the finishing gear train, which only partially satisfies the characteristics which have just been presented. without departing from the scope of the present invention.

For example, it is possible to provide that the non-circular wheels used go 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 turn since the torque available to the finishing gear is controlled.

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

Advantageously, it will be possible to provide a mechanism for stopping 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.

Furthermore, it will be noted that several mechanisms according to the present invention can be mounted in series in a watch movement, thus making it possible to increase the power reserve without having a torque available to the finishing gear too great.

Claims (11)

1. Mechanism, designed to deliver mechanical energy to a finishing geartrain in a clock movement in the form of a predefined output torque transmitted to a first mobile (20, 120) of the finishing geartrain, the mechanism comprising

   a barrel (1) mainspring (3) of which one end, the internal end, is secured to a barrel arbor (5, 105) and of which one end, the external end, is secured to a barrel drum (2, 102), a first of the said ends being intended to be kinematically connected to the first mobile of the finishing geartrain,

   a gear set designed to provide a kinematic connection between the said ends of the said barrel mainspring and allow a transfer of mechanical energy between said ends,

   the said gear set comprising 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 kinematically connected to a rewinding mechanism (7) for rewinding the said barrel mainspring (3),

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

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

   characterized in that the said planetary gear set (24, 26, 28, 30, 32, 34, 102, 126, 128, 130, 132, 134) comprises a planet (26, 126) comprising a first non-circular wheel (28, 128) arranged in mesh with a first non-circular solar wheel (30, 130).
2. Mechanism according to Claim 1, characterized in that the said non-circular wheels (28, 30, 128, 130) have respective peripheries such that the torque transmitted to the first mobile (20, 120) of the finishing geartrain is substantially constant.
3. Mechanism according to Claim 1 or 2, characterized in that the said output torque is transmitted to the finishing geartrain from the said barrel (1) drum (2, 102), the said planetary gear set (24, 26, 28, 30, 32, 34, 102, 126, 128, 130, 132, 134) being arranged in such a way as to allow a transfer of energy from the said external end of the said barrel mainspring (3) towards the said internal end.
4. Mechanism according to Claim 3, characterized in that the said planetary gear set (24, 26, 28, 30, 32, 34) comprises a planet carrier (24) intended to be kinematically connected to the rewinding mechanism (7) and carrying the said planet (26) of which the said first non-circular wheel (28) is secured to a second planetary wheel (32) and coaxial therewith, the said first non-circular planetary wheel (28) having a kinematic connection with the said barrel drum (2), the said first non-circular solar wheel (30) having a kinematic connection to the said barrel arbor (5).
5. Mechanism according to Claim 4, characterized in that the said first non-circular solar wheel (30) is coaxial with the said barrel arbor (5) being secured to rotate as one therewith.
6. Mechanism according to Claim 4 or 5, characterized in that it comprises a second solar wheel (34) secured to rotate as one with the said barrel drum (2) and arranged in mesh with the said second planetary wheel (32).
7. Mechanism according to Claim 3, characterized in that the said planetary gear set (102, 126, 128, 130, 132, 134) is also designed to allow a transfer of energy from the said internal end of the said barrel mainspring (3) towards the said external end or the finishing geartrain.
8. Mechanism according to Claim 7, characterized in that the said barrel drum (102) defines a planet carrier of the said planetary gear set, this carrier carrying the said planet (126) of which the said first non-circular wheel (128) is secured to a second non-circular planetary wheel (132) and coaxial therewith, the said first non-circular planetary wheel (128) having a kinematic connection to the said barrel arbor (105) via the said first non-circular solar wheel (130), the said second non-circular planetary wheel (132) being intended to have a kinematic connection to the rewinding mechanism (7) via a second non-circular solar wheel (134).
9. Mechanism according to Claim 8, characterized in that the said second non-circular solar wheel (134) is coaxial with the said barrel arbor (105) while being free to rotate with respect to the latter.
10. Clock movement comprising a mechanism according to any one of the preceding claims.
11. Timepiece comprising a clock movement according to Claim 10.

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