Timepiece movement

Abstract

The invention relates to a timepiece movement (1) comprising: - a mechanical energy source (3); - a constant-force device (7) comprising an input wheel (11), arranged to be driven by said mechanical energy source (3), as well as an output wheel (13) kinematically connected to said input wheel (11) via a resilient element (9), which is preloaded and arranged to be recharged periodically on the basis of the rotation of said output wheel (13); - a regulating system (5) arranged to be driven by said output wheel (13). According to the invention, said movement (1) comprises: - an activation mechanism (29) arranged to be driven by said output wheel (13) and to drive a supplementary mechanism (27); and - a preload control system (23) arranged to modify said preload of said resilient member (9) on the basis of the state of said activation mechanism (29).

Description

Technical field

[0001] The present invention relates to the field of watchmaking. It relates, more particularly, to a watch movement comprising a constant force mechanism as well as an additional disengageable mechanism, such as a chronograph mechanism, an animation, a chime, a countdown or the like. State of the art

[0002] In order to minimize variations in the torque received by the regulating system of a timepiece, a constant force mechanism (also called an "equality remontoir") is often incorporated into the kinematic chain linking the regulating system to the energy source, with the aim of improving isochronism.

[0003] These constant force mechanisms comprise a force input driven by the energy source and a force output that is kinematically linked to the input via an elastic element. The latter is subjected to a prestress and is intermittently tensioned during rotation of the output. To achieve this, a locking system is arranged to block the rotation of the input until the rotation of the output triggers a rotation of the input by a step of a predetermined angle.

[0004] In doing so, it is only the torque provided by the elastic element which drives the regulating system, this torque being relatively stable and independent of that provided by the energy source (provided that the latter torque remains sufficiently high to raise the elastic element).

[0005] A first classical version of such a constant force mechanism is revealed by document CH296060. In this construction, the input and output are coaxial and connected to each other by the elastic element. The input carries a satellite pinion which is supported on a fixed toothing and which is integral in rotation with a star which cooperates with a pin carried by the output so that the star is blocked and released periodically by the rotation of the output.

[0006] Another version of such a constant force mechanism uses a system inspired by an escapement, comprising a cam-driven anchor to release the rotation of the input according to the rotation of the output. An example of such a mechanism is disclosed by document EP2166419. In this document, the preload of the elastic element can easily be modified by the watchmaker to optimize the torque available at the output.

[0007] However, when the movement includes an additional disengageable mechanism, such as a chronograph mechanism, an animation, a chime or the like, the torque requirement varies depending on the condition of this additional mechanism.

[0008] One solution, proposed by document CH716126, is to arrange the power take-off for the additional mechanism kinematically upstream of the constant force mechanism. In doing so, the state of the additional mechanism does not influence the torque supplied to the regulating system. However, this solution is only compatible with constant force mechanisms whose input release frequency is relatively high, otherwise the frequency of the rotational steps of the power take-off may be insufficient to operate the additional mechanism. An example would be the case of a constant force device input release frequency of one step per two seconds. Such an arrangement would not be suitable for a chronograph mechanism driven by a power take-off located upstream of the constant force mechanism, since a chronograph must have a time resolution of at least one second, ideally a fraction of a second.

[0009] Document EP 1 445 669 A1 discloses a constant force mechanism for wristwatches.

[0010] The aim of the invention is therefore to provide a clockwork movement in which the aforementioned defects are at least partially overcome. Disclosure of the invention

[0011] More specifically, the invention relates to a clockwork movement as defined by claim 1. This movement comprises: a source of mechanical energy, such as one or more barrels housing one or more mainsprings; a constant force device of any kind comprising an input wheel, arranged to be driven by said source of mechanical energy, as well as an output wheel kinematically connected to said input wheel by means of an elastic element subjected to prestressing and arranged to be periodically recharged as a function of the rotation of said output wheel; a regulating system, such as an escapement-balance-hairspring assembly arranged to be driven by said output wheel.

[0012] According to the invention, said movement comprises: an activation mechanism, such as a clutch, arranged to be driven by said output wheel and to drive an additional mechanism such as a chronograph, an animation, a chime or the like; and a preload control system arranged to modify said preload of said elastic element depending on the state of said activation mechanism.

[0013] By these means, the preload of the elastic element can be modified depending on the state of the activation mechanism, i.e. depending on whether the additional mechanism is in operation or at rest. This makes it possible to minimize the influence of the additional mechanism on the torque received by the regulating system, while allowing the additional mechanism to be located kinematically downstream of the constant force device, in particular by means of an increase in said preload when the additional mechanism is in operation. Isochronism is thus ensured.

[0014] Advantageously, said prestress control system is arranged such that the angular ratio between one of the ends of said elastic element and either said input mobile or said output mobile can be modified depending on the state of said activation mechanism, which has the effect of modifying the prestress, by partially arming or disarming the elastic element.

[0015] Advantageously, the kinematic connection between said input mobile and said elastic element is provided by said prestressing control system. In particular, one end of said elastic element can be fixed to said output mobile, the other end of said elastic element being fixed to a control wheel arranged to be driven by said prestressing device.

[0016] Advantageously, the prestressing control system is arranged to make a kinematic connection between said input mobile and said control wheel such that: said pilot wheel can be driven in synchronism with said input wheel during normal operation of the movement, and the angular ratio between said pilot wheel and said input wheel can be modified so as to vary the prestress of the elastic element.

[0017] Advantageously, said prestressing control system comprises a differential gear comprising: a first input arranged to be driven by said input wheel; a second input arranged to be driven depending on the state of said activation mechanism; and an output arranged to drive said steering wheel.

[0018] Advantageously, said first input comprises a planet carrier mobile bearing a satellite pinion meshing both with a first sun wheel acting as said output and with a second sun wheel acting as said second input.

[0019] Advantageously, said output mobile is coaxial with said input mobile.

[0020] Advantageously, said input wheel is integral in rotation with a planet carrier wheel carrying a satellite pinion engaged with fixed teeth and integral in rotation with a star which cooperates with a pin carried by said output wheel so as to periodically release the rotation of said input. This arrangement therefore reproduces the operation of the mechanism proposed by document CH296060.

[0021] The clockwork movement according to the invention can, of course, be incorporated into a timepiece Brief description of the drawings

[0022] Other details of the invention will appear more clearly on reading the following description, given with reference to the appended drawings in which: Fig. 1 is a schematic view of a clockwork movement according to the invention; and Fig. 2 is a schematic view of part of the clockwork of the figure 1 , which illustrates a particular embodiment of the prestressing control system. Method of carrying out the invention

[0023] There figure 1schematically illustrates a watch movement 1 according to the invention, kinematic connections being mainly illustrated by arrows. Of course, the general knowledge of a person skilled in the art in the field of watchmaking allows him to create such kinematic connections by means of gears, cogs, belts, chains or by any appropriate means. In the present description, a kinematic connection or meshing may be direct or indirect, and the arrangement illustrated is not to be interpreted as being limiting.

[0024] The movement 1 comprises a mechanical energy source 3, such as one or more barrels, which drives a regulating system 5, such as an escapement-balance-hairspring assembly of any type, via a suitable kinematic connection. This kinematic connection comprises a constant force device 7, kinematically interposed between the energy source 3 and the regulating system 5. A display device 8 takes force from the kinematic connection in a known manner, this force take-off typically being kinematically located upstream of the constant force device 7. However, it cannot be excluded that the force take-off for all, or part, of the display device 8 is located downstream of the constant force device 8. For example, the force take-off for the display of the seconds could be arranged downstream, while that for the hours and minutes is located upstream of the constant force device.

[0025] In the illustrated embodiment, the constant force device 7 is based on that of document CH296060, but the same principle can also be applied to a constant force device 7 of the “escapement” type, such as for example that of document EP2166419 or to another type of mechanism of this type.

[0026] In all cases, the constant force device 7 comprises an elastic element 9 which is part of a kinematic connection between, on the one hand, an input wheel 11, which is driven directly or indirectly by the energy source, and, on the other hand, an output wheel 13, which is coaxial with said input wheel 11 and which directly or indirectly drives the regulating system 5. The elastic element 9 is subjected to a prestress and is arranged to be recharged periodically as a function of the rotation of said output wheel 13, as mentioned in the introduction. The elastic element 9 is typically a flat spiral-shaped spring, but may also be a leaf spring, a coil spring or the like.

[0027] In the illustrated embodiment, the constant force device 7 comprises a planet carrier wheel set 15 which is rotationally fixed to the input wheel set 11 (or alternatively acts as the input wheel set 11 itself) and which carries a planet wheel set 17 composed of a pinion 17a which meshes with a fixed toothing 19, as well as a star 17b which is rotationally fixed to the pinion 17a. This star cooperates with a pin 21 which is integral in rotation with said output wheel 13, such that a rotation of said output wheel 13 at a predetermined angle, under the effect of the elastic element 9, releases the star 17b, which causes a rotation of the planet carrier wheel 15 and thus of the input wheel 11 at a rate of said predetermined angle, the next point of the star 17b being blocked again by the pin 21 when the star 17b rolls on the fixed toothing 19.Document CH296060 contains a detailed explanation of this operation, in the context of a construction in which the elastic element 9 connects the input mobile 11 directly to said output mobile 13.

[0028] In the construction of document CH296060, the prestress of the elastic element 9 is fixed, and is predetermined by the watchmaker. On the other hand, in the illustrated embodiment, this prestress can be modified by means of a prestress control system 23.

[0029] For this purpose, instead of being connected directly to the input wheel 11, one of the ends of the elastic element 9 is mounted on a pilot wheel 25 which is mounted loose in the constant force device 7, the other end of the elastic element 9 being integral with the output wheel 13. In the illustrated embodiment, the outer end of the elastic element 9 is fixed to the pilot wheel 25, while the inner end is fixed to the output wheel 13, but the reverse configuration is also possible.

[0030] The prestressing control system 23 is arranged to make a kinematic connection between the input mobile 11 and the control wheel 25 such that: the pilot wheel 25 can be driven in synchronism with the input wheel 11 during normal operation of the movement, and the angular ratio between these two elements can be modified so as to vary the prestress of the elastic element 9.

[0031] The purpose of this preload control system 23 is to be able to compensate for the needs (such as torque and force) necessary for the additional disengageable mechanism 27, which is located kinematically downstream of the constant force device 7. This additional mechanism 27 may be, for example, a chronograph mechanism, an animation mechanism, a chime, a countdown or the like, driven by the output wheel set 13 by means of an activation mechanism 29 of any known type, such as for example a clutch of any type (radial, vertical, sliding pinion, etc.), a cam, a column wheel, a spring armed for a certain time which releases at a given moment, or the like. Since the specific form of the activation mechanism 29 is a clutch 29 in the embodiment the figure 1, the specific term “clutch 29” is subsequently used to indicate the generic characteristic “activation mechanism 29”, in order to simplify reading.

[0032] By positioning the additional mechanism in this way, the latter can benefit from a relatively high angular velocity whose angular step is independent of the constant force device 7, and therefore does not depend on the frequency of the rotation steps of the star 17b.

[0033] However, the torque requirement downstream of the constant force device 7 varies depending on the state of the additional mechanism 27. When the latter is not in operation and the clutch 29 is disengaged (more generically when the activation mechanism 29 is in the deactivated state), the torque requirement is lower, and the torque supplied to the regulating system 5 is thus higher, the latter receiving essentially all of the torque supplied by the constant force device 7. The beat frequency and amplitude of its oscillator are consequently higher.

[0034] When the clutch 29 is engaged (more generically when the activation mechanism 29 is in the activated state), the torque requirement is greater, and the torque available for driving the regulating system 5 is thus reduced since it is shared with the additional mechanism 27. The beat frequency and amplitude of the oscillator are thus reduced.

[0035] This situation is, of course, detrimental to isochronism, and reduces the positive effect of the constant force device 7 when the additional mechanism is in operation.

[0036] The preload control system 23 makes it possible to compensate for this variation in torque requirement, by varying the preload of the elastic element 9 as a function of the latter, in particular as a function of the state of the clutch 29.

[0037] Consequently, when the clutch 29 is disengaged, the pilot wheel 25 occupies a first relative angular position with respect to the input wheel 11, and the elastic element 9 is subjected to a first predetermined prestress.

[0038] When the clutch 29 is engaged, the pilot wheel 25 occupies a second relative angular position with respect to the input wheel 11, and the elastic element 9 is subjected to a second predetermined prestress, greater than said first prestress.

[0039] In the illustrated variant, the control of the clutch 29 and that of the preload control system 23 are carried out in parallel, by means of a common control device 31. It is also possible to arrange the control of these two elements in series. In any case, the control device 31 ensures that the angular position relative to the control wheel 25 with respect to the input wheel (and therefore the preload of the elastic element 9) changes according to the state of the clutch. Furthermore, the control device 31 can be of the manual type (actuated by a pusher, a bolt or similar), or of the automatic type (actuated by a mechanism internal to the movement 1).

[0040] There figure 2illustrates a non-limiting way of carrying out the modification of the prestress of the elastic element 9, which is based on a differential gear. In order to simplify this figure, the elements located kinematically downstream of the output mobile 13 have not been shown.

[0041] The prestressing control system 23 comprises a planet carrier wheel set 33 (which is specific to it and which is distinct from the planet carrier wheel set 15 of the constant force device 7) acting as a first input which meshes with the planet carrier wheel set 15 of the constant force device 7, as well as a first sun wheel set 35 which is coaxial with the planet carrier wheel set 33 and cooperates with the control wheel 25 via a reversing gear 37. The first sun wheel set 35 therefore acts as an output. A second sun wheel set 39, acting as a second input and being coaxial with the first 35, cooperates with, on the one hand, the control device 31, and on the other hand with at least one satellite wheel set 41, which meshes with each of the sun wheels 35, 39.Of course, the illustrated construction is not limiting, and the presence or absence of references between the elements of the constant force device 7 and those of the prestressing control system 23 can be determined according to the needs of the manufacturer, insofar as the gear ratios are appropriate.

[0042] During normal operation of the mechanism, the control device 31 maintains the second solar mobile 39 in a first predetermined angular position. The rotation of the planet carrier mobile 15, and therefore of the input mobile 11 which is integral with it in rotation, is thus transmitted to the pilot wheel 25, the gear ratios being chosen so that the angular speeds of these two elements are identical.

[0043] When the control device 31 is actuated, which, as a reminder, causes the clutch 29 to be engaged and disengaged and therefore the additional mechanism 27 to be started, the control device 31 causes the second solar mobile 39 to pivot in one direction or the other (as the case may be) to occupy a second predetermined angular position distinct from the first, and this by means of a cam, a lever, a rake or any other ad hoc means. This pivoting causes the satellite mobile 41 to pivot around its own axis of rotation and thus causes an additional rotation of the first solar mobile 35 at a predetermined angle in one direction or the other, and which is thus added to or subtracted from the normal rotation.This additional rotation is transmitted to the steering wheel 25, and is added to or subtracted from the rotation received from the planet carrier 15, thus modifying the angular ratio between these two elements and partially arming / disarming (if applicable) the elastic element 9, the prestress of which is thus modified.

[0044] Of course, other constructions of the prestressing control system 23 are possible and are within the reach of those skilled in the art, and the same principle can be applied to a constant force device 7 of the type disclosed by document EP2166419 or similar.

[0045] Although the invention has been previously described in connection with specific embodiments, other additional variations are also conceivable without departing from the scope of the invention as defined by the claims.

Claims

1. Timepiece movement (1) comprising : - a mechanical energy source (3) ; - a constant-force device (7) comprising an input mobile (11), arranged to be driven by said mechanical energy source (3), as well as an output mobile (13) kinematically linked to said input mobile (11) via an elastic element (9) subjected to a preload and arranged to be recharged periodically as a function of the rotation of said output mobile (13); - a regulating system (5) arranged to be driven by said output mobile (13); - an activation mechanism (29) arranged to be driven by said output mobile (13) and to drive a further mechanism (27); characterized in that the movement (1) comprises : - a preload control system (23) arranged to modify said preload of said elastic element (9) as a function of the state of said activation mechanism (29).

2. Timepiece movement (1) according to the preceding claim, wherein said preload control system (23) is arranged such that the angular relationship between, on the one hand, one of the ends of said elastic element (9) and, on the other hand, either said input mobile (11) or said output mobile (13), can be modified as a function of the state of said activation mechanism (29).

3. Timepiece movement (1) according to the preceding claim, wherein the kinematic connection between said input mobile (11) and said elastic element (9) is provided by said preload control system (23).

4. Timepiece movement (1) according to the preceding claim, wherein one end of said elastic element (9) is fixed to said output mobile (13), the other end of said elastic element (9) being fixed to a control wheel (25) arranged to be driven in rotation by said preloading device (23).

5. Timepiece movement (1) according to the preceding claim, wherein said preload control system (23) is arranged to make a kinematic connection between said input mobile (11) and said control wheel (25) such that : - said control wheel (25) can be driven in synchronism with said input mobile (11) during normal operation of the movement (1), and - the angular relationship between control wheel (25) and said input mobile (11) can be varied so as to vary said preload of the elastic element (9).

6. Timepiece movement (1) according to the preceding claim, wherein said preload control system (23) comprises a differential gear comprising : - a first input (33) arranged to be driven by said input mobile (11) ; - a second input (39) arranged to be driven as a function of the state of said activation mechanism (29); and - an output (35) arranged to drive said control wheel (25).

7. Timepiece movement (1) according to the preceding claim, wherein said first input (33) comprises a satellite-carrying mobile (33) carrying a satellite mobile (41) meshing both with a first sun gear (35), acting as said output, and with a second sun gear (39), acting as said second input (39).

8. Timepiece movement (1) according to one of the preceding claims, wherein said output mobile (13) is coaxial with said input mobile (11).

9. Clockwork movement (1) according to the preceding claim, in which the said input mobile (11) is fixed in rotation with a satellite-carrying mobile (15) carrying a satellite pinion (17a) in mesh with a fixed toothing (19) and fixed in rotation with a star (17b) which cooperates with a pin (21) carried by said output mobile (13) so as periodically to release the rotation of said input (11).

10. Timepiece movement (1) according to one of the preceding claims, wherein said activation mechanism (29) is a clutch.

11. Timepiece comprising a timepiece movement (1) according to one of the preceding claims.

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