Constant-force escapement mechanism for timepiece movement

Abstract

The invention relates to a constant-force escapement mechanism (1) for a timepiece comprising: - an escapement wheel (3) that has a plurality of teeth and is arranged to maintain a spring-balance oscillator (5, 7); - a winding wheel (11) that has a plurality of teeth and is arranged to be rotated by a drive source, the winding wheel (11) being connected to the escapement wheel (3) via a return element (21); - a locking pallet fork (25) that is pivotably mounted and arranged to move between a first stable angular position and a second stable angular position according to the rotation of the escapement wheel (3), and to lock and release the winding wheel (11) at a rate of one step in its rotation as the locking pallet fork (25) moves from one of its stable positions to the other. According to the invention, the escapement mechanism (1) further comprises a control wheel (15) that rotates as one with the escapement wheel (3) and is mounted so as to be angularly adjustable relative to the latter, the control wheel (15) having a plurality of teeth and being arranged to engage with the locking pallet fork (25) in order to move it between one of its stable positions to the other.

Description

Description CONSTANT FORCE ESCAPE MECHANISM FOR WATCH MOVEMENT Technical field

[0001] The present invention relates to the field of watchmaking. It concerns, more particularly, a constant force escapement mechanism. State of the art

[0002] The escapement mechanism that is the subject of the present invention is based on that initially disclosed by document CH353679 and further developed in document CH704275. Furthermore, an escapement of this type was also used in a piece produced by Fabrication de Montres Normandes in 2009 (see https: / / forurnarnontres.forurnactif.com / t68941-fabrication-de-montres-normandes).

[0003] In this type of escapement, the escape wheel is coaxial with a rewinding wheel, which at first glance appears to be an additional escape wheel. The rewinding wheel is integral in rotation with a wheel or pinion which receives the torque coming from the barrel, while the escape wheel is mounted freely around the same geometric axis. These two wheels are connected to each other by means of an elastic return element, so that the escape wheel is driven in rotation by the latter.

[0004] The escape wheel cooperates with an anchor in a conventional manner, and also cooperates with a locking lever which has two levels of pallets, the pallets of a first level of which cooperate with the teeth of the escape wheel while the pallets of a second level cooperate with those of the rewinding wheel in order to lock and release them alternately when it moves from one of its stable positions to the other.

[0005] After each release of the anchor and during the pivoting of the escape wheel, one of the teeth of the latter comes into contact with one of the pallets of the first level in order to trigger a pivoting of the blocking lever from one of its stable positions to the other. In doing so, the rewinding wheel pivots under the effect of the mainspring stored in the barrel and winds the elastic element, before being relocked by the blocking lever.

[0006] In doing so, during operation of the escapement, the rewinding wheel advances in steps in synchronism with the escape wheel, which ensures that the force provided by the elastic element remains substantially constant and that the escapement is not subject to torque variations when the mainspring is unwinding. Since the advances of the rewinding wheel take place between those of the escape wheel with an angular and temporal offset, the latter take place when the anchor is not cooperating with the balance, which minimises or eliminates the disturbance of the latter.

[0007] A first disadvantage of this system is that the moment of release of the locking lever relative to that of the escape wheel is predetermined by the geometry of the locking lever (including its pallets) as well as by the positioning of its pivot axis. Consequently, it is impossible to adjust the moment of release of the rewinding wheel (and therefore its phase shift relative to the escape wheel) other than by modifying the geometry of the locking lever. Secondly, the angular movements of the locking lever impair the operation of the escapement. Indeed, when the lever reaches the stop, shocks occur which cause it to bounce.

[0008] Document CH 120028 reveals a constant force escapement in which the rewinding wheel is a three-pointed star locked and released by a locking lever controlled by a constant radius cam rotating integrally with the escape wheel. The constant radius cam is a single piece with an axle, on which the escape wheel is riveted. This arrangement, as well as those disclosed by documents US2970427 and FR1009853, present the same defects as mentioned above.

[0009] The aim of the invention is therefore to provide a constant force escapement mechanism in which the aforementioned defects are at least partially overcome. Disclosure of the invention

[0010] More specifically, the invention relates to a constant force escapement mechanism for a timepiece, as defined in a first independent claim. This mechanism comprises:

[0011] - an escape wheel having a plurality of teeth and arranged to maintain a sprung balance oscillator in a known manner, typically by means of a Swiss anchor or other means;

[0012] - a rewinding wheel having a plurality of teeth and arranged to be driven in rotation by a driving source such as a mainspring housed in a barrel or any other known driving source, said rewinding wheel being connected to said escapement wheel by means of a return element, which may be formed by a spiral spring, another type of spring, a flexible guidance system integrated into one or other of these wheels, or any other suitable element;

[0013] - a locking lever pivotally mounted around a physical or virtual axis and arranged to move between a first and a second stable angular position as a function of the rotation of said escape wheel, and to lock and release said rewinding wheel at the rate of one step of its rotation (i.e. typically at the rate of half a step of its teeth) during its movement from one of its stable positions to the other.

[0014] According to a first aspect of the invention, said escapement mechanism further comprises a control wheel mounted integral in rotation with said escapement wheel and angularly adjustable relative to the latter, said control wheel having a plurality of teeth and being arranged to cooperate with said locking lever in order to move it between one of its stable positions to the other. Typically, the profile of all said teeth is identical, and each wheel has the same number of teeth, but this does not necessarily have to be the case.

[0015] Since the angular position of the control wheel can be adjusted relative to the escape wheel, the exact moment of release of the blocking lever can be varied by the watchmaker to optimize the operation of the escapement mechanism for each individual escapement, thereby improving efficiency and / or rate.

[0016] Advantageously, said control wheel is arranged between said escapement wheel and said rewinding wheel, which represents the simplest solution to implement, but other configurations of the three wheels are also possible.

[0017] Advantageously, said resetting wheel is integral in rotation with a pinion arranged to be driven in rotation by said drive source, said pinion being extended by an axis around which is mounted freely in rotation an assembly comprising said control wheel and said escape wheel.

[0018] Advantageously, said escape wheel is made integral in rotation with said control wheel by means of at least one adjustment screw or by greasy friction by means of a friction element.

[0019] Advantageously, said locking lever has a plurality of pallets arranged to cooperate with the resetting wheel on the one hand, and the control wheel on the other hand, each pallet having a trapezoidal section. This allows the use of the same standard pallets for each pallet.

[0020] Advantageously, the teeth of the escape wheel, the rewinding wheel and the control wheel are substantially identical, or alternatively simply have the same number of teeth but with different profiles.

[0021] In another variant, said rewinding wheel has the same number of teeth as said control wheel, but a smaller number of teeth than said escapement wheel. In such a case, the teeth of the rewinding wheel and the control wheel are regularly distributed around each wheel and have the same theoretical tooth pitch as the escape wheel, but some teeth have been omitted. In doing so, the locking lever is triggered after a predetermined number of steps of the escape wheel instead of every step of the latter.

[0022] According to another aspect, the invention also relates to a constant force escapement mechanism for a timepiece, as defined in a second independent claim. This escapement mechanism comprises:

[0023] - an escape wheel having a plurality of teeth and arranged to maintain a sprung balance oscillator in a known manner, typically by means of a Swiss anchor or other means;

[0024] - a rewinding wheel having a plurality of teeth and arranged to be driven in rotation by a driving source such as a mainspring housed in a barrel, said rewinding wheel being connected to said escapement wheel by means of a return element, which may be formed by a spiral spring, another type of spring, a flexible guidance system integrated into one or other of these wheels, or any other suitable element;

[0025] - a locking lever pivotally mounted around a physical or virtual axis and arranged to move between a first and a second stable angular position as a function of the rotation of said escape wheel, and to lock and release said rewinding wheel at the rate of one step of its rotation (i.e. typically at the rate of half a step of its teeth) during its movement from one of its stable positions to the other.

[0026] According to this aspect of the invention, said locking lever cooperates with a flywheel which is distinct from the balance-spring oscillator, that is to say that it is a separate and independent part of this assembly and which is therefore neither the balance nor its plate. Typically, the flywheel is not coaxial with the balance-spring oscillator.

[0027] This flywheel increases the effective inertia of the locking lever and smooths its movements, which improves the operation of the escapement compared to those of the prior art cited above.

[0028] Advantageously, said flywheel is a plate mounted in rotation, typically on a frame element. This can in particular allow the use of standard components already available, in particular balance wheel plates. Typically, said plate comprises a pin which cooperates with a fork which comprises said locking lever.

[0029] Advantageously, said locking lever takes the form of an anchor. Again, this allows the use of standard components that are already available.

[0030] Of course, both aspects of the invention can be combined in a single escapement mechanism. Brief description of the drawings

[0031] Other details of the invention will appear more clearly on reading the following description, given with reference to the appended drawings in which: - Figure 1 is an isometric view of a first embodiment of an escapement mechanism according to the invention; - Figure 2 is a cutaway isometric view of the wheel stack of the embodiment of Figure 1; - Figure 3 is a partial isometric view of a second embodiment of an escapement mechanism according to the invention. Embodiments of the invention

[0032] Figure 1 illustrates a first embodiment of an escapement mechanism 1 according to the invention, while Figure 2 illustrates the particular arrangement of the wheels that the mechanism 1 comprises.

[0033] This mechanism 1 comprises an escape wheel 3 pivotally mounted around an axis A1 and arranged to maintain the oscillation of a balance oscillator 5 - balance spring 7 arranged in such a way that said balance spring 7 exerts a restoring torque on said balance 5 so as to make the latter oscillate around a neutral point, in a known manner.

[0034] In the illustrated embodiment, the escape wheel 3 cooperates with a Swiss-type anchor 9 pivotally mounted around an axis A2. This escape wheel 3 is arranged to be blocked and released by the anchor 9, as well as to provide impulses to the balance wheel 5 in a known manner. However, a detent system, an Omega-Daniels escapement or any other type of escapement known to those skilled in the art may be used. In doing so, the assembly consisting of escapement mechanism 1 - balance wheel 5 - balance spring 7 forms a regulating system.

[0035] The escape wheel 3 is coaxial with a rewinding wheel 11, which has a plurality of teeth and is rotationally secured to a pinion 13 which serves as a force input from the driving source (not shown, typically a barrel housing a mainspring in a known manner). This pinion 13 acts as an escape pinion, and is kinematically connected to said driving source by an ad hoc gear train (typically called a “finishing gear train”).

[0036] The escape wheel 3 is integral in rotation with a control wheel 15, which can be angularly offset relative to the escape wheel 3. In the illustrated embodiment, adjusting screws 17 serve to make the two wheels 3, 15 integral in rotation, but by unscrewing them, the watchmaker can move one of these wheels 3, 15 angularly relative to the other for reasons which will become more clearly apparent later. Alternatively, the two wheels 3, 15 can be mounted with greasy friction relative to each other, provided that the latter remain integral in rotation during normal operation of the escapement 1. Any known type of friction connection between the wheels 3 and 15 can be envisaged, provided that the friction torque is dimensioned accordingly.

[0037] The assembly comprising the escape wheel 3 and the control wheel 15 is mounted to rotate freely relative to the assembly comprising the rewinding wheel 11 and the pinion 13. For this purpose, the pinion 13 is extended by an axis 13a which extends through the wheels 3, 15, and supports this assembly. between first bearings 18. The assembly comprising the wheels 3, 15 is mounted to pivot freely around this axis 13a by means of second bearings 19 which surround the latter.

[0038] The rewinding wheel 11 is connected to the escape wheel 3 by means of a return element 21, here a spiral spring, which is prestressed in order to provide sufficient torque to pivot the escape wheel 3 and maintain the oscillator 5, 7. For this purpose, the inner end of the return element 21 is rotationally fixed to the axis 13a (which is, as a reminder, rotationally fixed to the rewinding wheel 11), while its outer end is fixed to a stud 3a integral with the escape wheel 3. Consequently, the assembly comprising the two wheels 3, 15 is kinematically connected to the assembly comprising the rewinding wheel 11 and the pinion 13 by means of this return element 21, which ensures that the torque to which the escape wheel 3 is subjected remains substantially constant as long as the return element 21 can be recharged. by the driving source.

[0039] In the illustrated construction, the control wheel 15 is interposed between the escape wheel 3 and the rewinding wheel 11, and although the illustrated construction is the simplest to implement, the stacking of the wheels 3, 11, 15 along the axis A1 can be defined differently. Indeed, one or the other of the wheels 3, 11 can be in the middle, and the control wheel 15 can be on one side or the other. For this purpose, provided that the set of wheels 3, 15 is connected to the set of the rewinding wheel 11 and to the pinion 13 via the return element 21, the connection between these two sets can be arranged ad hoc, according to the needs of the manufacturer. For example, one end of the return element 21 can be fixed to one or other of the wheels 3, 15, while its other end can be fixed to the wheel 3 directly or to the axle 13a, depending on the configuration chosen.Furthermore, the return element 21 can alternatively be integrated into one or other (or even several) of the wheels 3, 11, 15 (in particular the resetting wheel 11 and / or the control wheel. 15), being made up of flexible elements (such as flexible blades) arranged in an ad hoc manner.

[0040] In order to maintain the preload of the return element 21 in the case where the driving source no longer provides enough torque to the pinion 13 to completely wind the return element 21, a stud 23 carried by the escape wheel 3 - control wheel 15 assembly is provided, this stud 23 taking place in a slot 11a which the rewinding wheel comprises in order to limit the angular phase shift between the wheels 3 and 11 as well as to maintain the initial pre-winding of the return element 21. Of course, other arrangements making it possible to limit the angular difference between the two assemblies 11, 13 respectively 3, 15 are also possible in order to obtain the same result, for example that used in document CH704275.

[0041] A locking lever 25 is arranged to lock and release the rewinding wheel 11 under the control of the control wheel 15, which pivots in accordance with the escape wheel 3. For this purpose, the locking lever 25 is pivotally mounted about an axis of rotation A3 (which may be a traditional physical axis or a virtual axis in the case where the locking lever 25 is supported by a flexible guide), which is distinct from the axis A2, such that it is arranged to pivot between a first and a second stable position (extreme positions), and comprises two pairs of pallets 25a, 25b, located on two different levels in order to cooperate respectively with the rewinding wheel 11 and the control wheel 15. The pallets 25a, 25b may take any ad hoc shapes, and may be integral with the locking lever 25 or be constituted by elements added to the latter.In the non-limiting embodiment illustrated, they each take a conventional trapezoidal shape (i.e. a section perpendicular to the axis A3 which is trapezoidal), similar to that of a Swiss lever escapement. In other words, they each comprise straight flanks linked by an end face forming an oblique impulse plane. The pallets 25a of the first level have a sufficient length so that a straight flank of. each pallet can block the teeth of the rewinding wheel 11 when the blocking lever 25 is in a corresponding extreme angular position, a flank of one of the pallets 25a thus being in the path of the latter. However, the pallets 25b are shorter than the pallets 25a (i.e. they extend less far from the blocking lever 25 than the latter), so that only their oblique ends can enter the path of the teeth of the control wheel 15 when the stopping lever 25 is in a respective extreme angular position.As is the case for the pallets of an anchor, the flank of each pallet 25a, 25b, which is located upstream (considered with respect to the direction of rotation of the wheels 3, 11, 15), is shorter than that which is located downstream, such that the end face is configured to pivot the locking lever 25 when the teeth of the wheels 11, 15 cooperate with the end flanks of the pallets 25a, 25b.

[0042] The operation of the escapement is therefore as follows:

[0043] At rest, the escape wheel 3 is blocked by a flank of one of the pallets 9a of the anchor 9, and the rewinding wheel 11 is also blocked by a flank of one of the pallets 25a of the first level.

[0044] When the anchor 9 releases a tooth of the escape wheel 3 under the effect of the rotation of the balance, the latter is free to pivot under the effect of the return element 21 until the flank of the other pallet 9a of the anchor stops it, in a known manner. The control wheel 15 being integral in rotation with the escape wheel 3, it also pivots.

[0045] During this pivoting, a tooth of the control wheel 15 comes into contact with the end face of the pallet 25b which is adjacent to the pallet 25a which is engaged with a tooth of the rewinding wheel 11. The cooperation between the tooth of the control wheel 15 and the oblique end face of the pallet 25b in question causes the locking lever 25 to be raised, which causes the pallet 25a to be released from the tooth of the rewinding wheel 11 and the pivoting of the latter under the effect of the motor spring.

[0046] A cooperation between the tooth of the rewinding wheel 11, which has just been released, and the oblique end face of the pallet 25a contributes to accelerating the pivoting of the locking lever 25, and the side of the other pallet 25a of the first level blocks the rotation of the resetting wheel 11.

[0047] By adjusting the angular position of the control wheel 15 relative to the escape wheel 3, the watchmaker can determine the moment in the cycle at which the blocking lever 25 is pivoted in order to optimize the performance of the escapement mechanism 1, by optimizing the time lapse between the release of the escape wheel 3 and that of the rewinding wheel 11. Since the control wheel 15 is integral in rotation with the escape wheel 3, the releases of the rewinding wheel 11 are always made according to the rotations of the escape wheel 3, even if it is the teeth of the control wheel 15 which control the pivoting of the blocking lever 25.

[0048] In order to smooth the operation of the locking lever 25, the latter takes the form of an anchor, the rod 25c of which carries a fork 25d which cooperates with a pin (not visible) of a plate 27 of a type which is well known in the context of a balance wheel, pivoted between standard bearings 28. The latter acts as a flywheel and makes it possible to increase the effective inertia of the locking lever 25 and to smooth its movements, which improves the operation of the escapement 1 compared to those of documents CH353679 and CH704275. This flywheel makes it possible to counterbalance the dynamic effects of shocks during the rebounds of the locking lever, in particular when it comes into abutment against the limiting pins 29 or during fork-ellipse contacts.

[0049] However, it is also possible to use a simple lever for the locking lever 25, as is the case in documents CH353679 and CH704275, or any other form of lever adapted accordingly.

[0050] Figure 3, in which only the main reference signs have been used and certain elements (including the return element 21) have been omitted, illustrates another embodiment of an escapement mechanism 1 according to the invention. The latter differs from that of Figure 1 with regard to the positioning of the axis A2 relative to the axis A1. In the embodiment embodiment of figure 1, the angle between the straight lines connecting the axes A2-A1 and A3-A1, is obtuse, in that of figure 3 it is acute, so that the two axes A2, A3 are on the same side of the mechanism, considered in the plane of the latter.

[0051] In a variant not illustrated, it is also possible for the axes A2 and A3 to be merged, so that the anchor 9 and the locking lever 25 are coaxial and superimposed.

[0052] It will be noted that, in the illustrated embodiments, the three wheels 3, 11, 15 may be substantially identical, or at least have substantially identical tooth shapes. Furthermore, the anchor 9 and the locking lever 25 may also be identical, with the exception of an added or thickened part to carry one of the pairs of pallets 25a, 25b. Even more, the pallets 9a, 25a, 25b may be of conventional and identical shape, with the exception of the length of the pallets 25b. The number of different parts to be manufactured can thus be minimized. The shape of the toothing of the control wheel 15 and / or the resetting wheel 11 may be chosen at will, and does not necessarily have to be conventional.Furthermore, the resetting wheel 11 and / or the control wheel 15 may be constituted by any type of element suitable for producing the described operation, such as for example a wheel with edge teeth, a wheel in which the teeth are constituted by pins, fingers or the like, "teeth" therefore being understood in the broad sense to encompass all the less common variations known to those skilled in the art. The wheels 11, 15, or the wheels 3, 15, may also be made of one material from the other, the connection between the two being by means of flexible elements, such as flexible blades. In the case where the wheels 11, 15 are made of one material, the flexible elements connecting them may also serve as a return element 21.

[0053] For the surplus, by reducing the number of teeth of the rewinding wheel 11 and removing one out of two from the control wheel 15, or two out of three, three out of four, four out of five etc. in relation to the teeth of the wheel escapement 3, the number of vibrations of the balance between each rewinding of the return element 21 can be increased, in a similar manner to a remontoir d'égalité.

[0054] As regards the materials, the entire range of materials used in contemporary watchmaking can be considered (metals, non-metals such as silicon, silicon compounds, synthetic diamond, sapphire, structurable glasses, ceramics, glass-ceramics, metallic glasses, polymers, composites, materials capable of additive manufacturing, etc.), and it should be noted that the pallets 9a, 25a, 25b may not only be separate parts added to the anchor 9, respectively the lever 25, but may be made in one piece with the latter.

[0055] The escapement mechanism 1 according to the invention is also compatible with an inclined balance wheel and is capable of being integrated into a tourbillon mechanism, whether of the mono-, bi- or triaxial type, but also into a carousel mechanism.

[0056] This description has been given as a non-limiting illustration of the invention. Those skilled in the art may add additions within its scope, without, however, departing from the scope of the invention defined by the claims.

Claims

Claims 1. Constant force escapement mechanism (1) for a timepiece, comprising: - an escape wheel (3) having a plurality of teeth and arranged to maintain a balance-spring oscillator (5, 7); - a rewinding wheel (11) having a plurality of teeth and arranged to be driven in rotation by a drive source, said rewinding wheel (11) being connected to said escapement wheel (3) via a return element (21); - a locking lever (25) pivotally mounted and arranged to move between a first and a second stable angular position as a function of the rotation of said escape wheel (3), and to lock and release said rewinding wheel (11) at the rate of one step of its rotation during the movement of said locking lever (25) from one of its stable positions to the other; characterized in that said escapement mechanism (1) further comprises a control wheel (15) mounted integral in rotation with said escape wheel (3) and angularly adjustable relative to the latter, said control wheel (15) having a plurality of teeth and being arranged to cooperate with said locking lever (25) in order to move it between one of its stable positions to the other.

2. Escapement mechanism (1) according to the preceding claim, wherein said control wheel (15) is arranged between said escape wheel (3) and said rewinding wheel (11).

3. Escapement mechanism (1) according to one of the preceding claims, in which said rewinding wheel (11) is integral in rotation with a pinion (13) arranged to be driven in rotation by said driving source, said pinion being extended by an axis (13a) around which is mounted freely in rotation an assembly comprising said control wheel (15) and said escape wheel (3).

4. Escapement mechanism (1) according to one of the preceding claims, in which said escapement wheel (3) is made integral in rotation with said control wheel by means of at least one adjustment screw (17) or by greasy friction.

5. Escapement mechanism (1) according to one of the preceding claims, wherein said locking lever (25) has a plurality of pallets (25a, 25b) arranged to cooperate with said rewinding (11) and release (15) wheels, each pallet (25a, 25b) having a trapezoidal section.

6. Escapement mechanism (1) according to one of the preceding claims, in which the teeth of the escape wheel (3), the rewinding wheel (11) and the control wheel (15) are substantially identical.

7. Escapement mechanism (1) according to one of claims 1 to 5, wherein said rewinding wheel (11) has the same number of teeth as said control wheel (15), but a lower number of teeth than said escape wheel (3).

8. Constant force escapement mechanism (1) for a timepiece, comprising: - an escape wheel (3) having a plurality of teeth and arranged to maintain a balance-spring oscillator (5, 7); - a rewinding wheel (11) having a plurality of teeth and arranged to be driven in rotation by a drive source, said rewinding wheel (11) being connected to said escapement wheel (3) via a return element (21); - a locking lever (25) pivotally mounted and arranged to move between a first and a second stable angular position as a function of the rotation of said escape wheel (3), and to lock and release said rewinding wheel (11) at the rate of one step of its rotation during the movement of said locking lever (25) from one of its stable positions to the other; characterized in that said locking lever (25) cooperates with a flywheel (27) which is separate from the sprung balance oscillator (5, 7).

9. Escapement mechanism (1) according to the preceding claim, wherein said flywheel (27) is a plate (27) mounted in rotation.

10. Escapement mechanism (1) according to the preceding claim, in which said plate (27) comprises a pin which cooperates with a fork (25d) which said locking lever (25) comprises.

11. Escapement mechanism (1) according to the preceding claim, wherein said locking lever (25) takes the form of an anchor.

12. Escapement mechanism (1) according to one of claims 1 to 7 and according to one of claims 8 to 11.

13. Regulating system comprising an escapement mechanism (1) according to one of the preceding claims as well as a balance (5) arranged to cooperate with said anchor and a spiral spring (7) arranged to exert a return torque on said balance (5).

14. Watch movement comprising a regulating system according to the preceding claim.

15. Timepiece comprising a watch movement according to the preceding claim.

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