Patent Grant
11493882
The invention concerns a timepiece regulating mechanism, comprising, arranged on a main plate, a resonator mechanism with a quality factor Q, and an escapement mechanism which is subjected to the torque of drive means comprised in a movement, said resonator mechanism comprising an inertia element arranged to oscillate with respect to said plate, said inertia element being subjected to the action of elastic return means directly or indirectly fixed to said plate, and said inertia element being arranged to cooperate with an escape wheel set comprised in said escapement mechanism.
The invention also concerns a timepiece movement comprising drive means, and such a regulating mechanism, whose escapement mechanism is subjected to the torque of these drive means.
The invention also concerns a watch, more particularly a mechanical watch, including such a movement, and/or such a regulating mechanism.
The invention concerns the field of timepiece regulating mechanisms, in particular for watches.
Most mechanical watches include a balance/balance spring type oscillator, cooperating with a Swiss lever escapement. The balance/balance spring forms the time base of the watch. This is called the resonator here. The escapement performs two main functions, namely maintaining the back and forth motions of the resonator and counting these back and forth motions. The escapement must be robust, not disturb the balance far from its point of equilibrium, resist shocks, avoid jamming the movement (for example, in the event of overbanking), and thus forms a vital component of the timepiece movement.
Typically, a balance/balance spring oscillates with an amplitude of 300°, and the angle of lift is 50°. The angle of lift is the angle through which the balance travels as the lever fork interacts with the impulse pin, also called the roller-pin, of the balance. In most current Swiss lever escapements, the angle of lift is divided either side of the point of equilibrium of the balance (+/−25°), and the lever tilts by +/−7°.
The Swiss lever escapement belongs to the detached escapement category, since, beyond the half-angle of lift, the resonator no longer touches the lever. This characteristic is essential for obtaining good chronometric properties.
A mechanical resonator includes an inertia element, a guide member and an elastic return element. Conventionally, the balance forms the inertia element, and the balance spring forms the elastic return element. The balance is guided in rotation by pivots which rotate in smooth ruby bearings. The associated friction causes energy losses and disruptions of rate. It is sought to remove these disruptions, which, moreover, depend on the orientation of the watch in the field of gravity. Losses are characterized by the quality factor Q of the resonator. It is also generally to sought to maximise this quality factor Q, in order to obtain the best possible power reserve. It is clear that the guide member is an essential factor in losses.
The use of a rotary flexure bearing, instead of the pivots and conventional balance spring, is a solution that maximises the quality factor Q. Flexible strip resonators, provided they are well designed, have promising chronometric properties, independently of orientation in the field of gravity, and have high quality factors, particularly due to the absence of pivot friction. Further, the use of flexure bearings eliminates problems of wear of the pivots.
However, the flexible strips generally used in such rotary flexure bearings are stiffer than balance springs. This results in work at higher frequency, for example on the order of 20 Hz, and with a lower amplitude, for example 10° to 20°. This at first sight seems incompatible with a Swiss lever type escapement.
An operating amplitude compatible with a resonator with rotary flexure bearings, particularly with strips, is typically from 6° to 15°. This results in a certain angle of lift value, which must be twice the minimum operating amplitude.
In the absence of particular precautions, an escapement with a small angle of lift may have mediocre efficiency and cause too great a losing rate. However, the combination of a high frequency and a low amplitude makes possible speeds of motion of the balance which are acceptable, without being too high, and thus the efficiency of the escapement is not automatically mediocre.
The resonator must have acceptable dimensions, compatible with being housed inside a timepiece movement. It is not possible, to date, to make a rotary flexure bearing of very large diameter, or having several pairs of levels of strips, which, theoretically, by placing successive flexure bearings in series, would allow an oscillation amplitude of the inertia element of several tens of degrees: therefore a flexure bearing with one or two levels of strips at most should be used, for example as known from EP Patent No. 3035126 in the name of THE SWATCH GROUP RESEARCH AND DEVELOPMENT Ltd.
In short, the effect of choosing a rotary flexure bearing is that the amplitude of the balance is reduced, and it is no longer possible to use a conventional Swiss lever escapement, which requires a balance amplitude that is considerably higher than half the angle of lift, i.e higher than 25°. A regulator comprising a resonator with flexure bearings thus requires a particular escapement mechanism, of different dimensioning from that of a normal Swiss lever escapement devised to operate with the same inertia element of the resonator.
It is an overall object of the present invention to increase the power reserve and precision of current mechanical watches. To achieve this object, the invention combines a resonator having rotary flexure bearings with a lever escapement optimised to maintain acceptable dynamic losses and to limit the chronometric effect of the unlocking phase.
In the absence of teaching in the prior art as to the dimensioning of both the resonator and the escapement mechanism, analytical model calculations and a series of simulations have revealed parameters for the resonator and escapement that are compatible with an acceptable loss and acceptable efficiency.
These calculations and simulations demonstrate that the ratio between the inertia of the inertia element, particularly a balance, and the inertia of the pallet lever, is determinant.
To this end, the invention concerns a regulating mechanism according to claim 1.
These resonators with rotary flexure bearings have very high quality factors, for example on the order of 3000, compared to a quality factor of 200 for a normal watch. Dynamic losses (kinetic energy from the escape wheel and pallet lever at the end of the impulse) are independent of the quality factor. These losses may thus become too high with a high quality factor, in relative terms, in comparison to the energy transmitted to the balance.
For proper operation of the mechanism, an impulse pin integral with the inertia element must penetrate up to a certain value, referred to as ‘depth’, the opening in the lever fork. Likewise, to ensure safety during the unlocking phase, once the impulse pin is unlocked, it must then be able to be kept at a certain distance, called the safety distance, from the horn of the fork opposite to the horn with which it was in contact immediately prior to being unlocked.
Thus, the invention further endeavours to impose a particular relation between the dimensions of the lever fork, the depth and safety distance values, and the values of the angles of lift of the lever and of the inertia element, to ensure that the impulse pin is properly removed from the fork, once travel through the half-angle of lift is complete.
The invention also concerns a timepiece movement comprising drive means, and such a regulating mechanism, whose escapement mechanism is subjected to the torque of these drive means.
The invention also concerns a watch, more particularly a mechanical watch, including such a movement, and/or such a regulating mechanism.
Other features and advantages of the invention will appear upon reading the following detailed description, with reference to the annexed drawings, in which:
The invention combines a resonator having a rotary flexure bearing, to increase the power reserve and precision, with an optimised lever escapement to maintain acceptable dynamic losses and to limit the chronometric effect of the unlocking phase.
The invention therefore concerns a timepiece regulating mechanism 300, comprising, arranged on a main plate 1, a resonator mechanism 100 with a quality factor Q, rotating about a main axis DP, and an escapement mechanism 200, which is subjected to the torque of drive means 400, comprised in a movement 500.
This resonator mechanism 100 includes at least one inertia element 2 which is arranged to oscillate with respect to plate 1, about a main axis DP. This inertia element 2 is subjected to the action of elastic return means 3 directly or indirectly secured to plate 1. Inertia element 2 is arranged to cooperate indirectly with an escape wheel set 4, particularly an escape wheel, which is comprised in escapement mechanism 200 and pivots about an escapement axis DE.
According to the invention, these elastic return means 3 include at least two flexible strips 5, to which is suspended the at least one inertia element 2, particularly a balance or suchlike, and which define a flexure bearing with a virtual pivot for this at least one inertia element 2. This at least one inertia element 2 carries an integral impulse pin 6. Escapement mechanism 200 includes a lever 7 arranged to pivot about a secondary axis DS and including a lever fork 8 which is arranged to cooperate with impulse pin 6. This escapement mechanism 200 is a detached escapement mechanism, wherein, during the operating cycle, resonator mechanism 100 has at least one phase of freedom in which pin 6 is at a distance from lever fork 8.
According to the invention, during each vibration, in a contact phase, pin 6 penetrates lever fork 8 with a depth of travel P greater than or equal to 40 micrometres and less than or equal to 200 micrometres, and in an unlocking phase, pin 6 remains at a distance from lever fork 8 with a safety distance S greater than or equal to 10 micrometres, and less than or equal to 60 micrometres. Impulse pin 6 and lever fork 8 are dimensioned such that the width L of lever fork 8 is greater than (P+S)/sin(α/2+β/2), depth of travel P and safety distance S being measured radially with respect to main axis DP, where α is the angle of lift of the lever which corresponds to the maximum angular travel of lever fork 8, and where β is the angle of lift of the resonator, during which pin 6 is in contact with lever fork 8.
More particularly, depth of travel P is greater than or equal to 80 micrometres and less than or equal to 120 micrometres.
More particularly still, depth of travel P is greater than or equal to 100 micrometres.
More particularly still, safety distance S is greater than or equal to 20 micrometres and less than or equal to 30 micrometres.
More particularly still, safety distance S is greater than or equal to 25 micrometres.
More particularly, the lift angle α of the lever is greater than or equal to 5° and less than or equal to 30°.
More particularly still, the lift angle α of the lever is less than or equal to 20°.
More particularly, the lift angle α of the lever is greater than or equal to 12° and less than or equal to 16°.
More particularly, the lift angle β of the resonator is greater than or equal to 3° and less than or equal to 30°.
More particularly, the lift angle β of the resonator is greater than or equal to 8° and less than or equal to 12°.
More particularly still, the lift angle β of the resonator is less than or equal to 10°.
More particularly, lever 7 forms a bistable stop device
Taking a specific escapement geometry and a specific operating amplitude, in particular 8°, it is possible with dynamic multi-body simulations (i.e. relating to a set of several components, each of which is assigned a particular mass and inertia distribution) to evaluate the efficiency and loss of this escapement mechanism as a function of the inertia ratio between the inertia of the inertia element and the inertia of the lever, which cannot be established using normal kinematic simulations. As seen in
The analytical model of the system thus showed that, if one wishes to limit dynamic losses, a particular condition links the inertia of the lever, the inertia of the inertia element, the resonator quality factor, and the angles of lift of the lever and of the inertia element: for a dynamic loss coefficient £, the inertia IB of all the inertia elements 2 with respect to main axis DP, on the one hand, and the inertia IA of lever 7 with respect to secondary axis DS on the other hand, are such that the ratio IB/IA is greater than 2Q·α2/(ε·π·β2), where α is the lift angle of the lever which corresponds to the maximum angular travel of lever fork 8.
More particularly, if one wishes to limit dynamic losses to a factor c=10%, the inertia IB of this at least one inertia element 2 with respect to main axis DP on the one hand, and the inertia IA of lever 7 with respect to secondary axis DS on the other hand, are such that the ratio IB/IA is greater than 2Q·α2/(0.1·π·β2), where α is the lift angle of the lever which corresponds to the maximum angular travel of lever fork 8.
More particularly, the lift angle β of the resonator, which is an overall angle, taken from both sides of the rest position, is less than twice the angle of amplitude by which inertia element 2 deviates furthest, in only one direction of motion, from a rest position.
More particularly, the angle of amplitude by which inertia element 2 deviates furthest from a rest position, is comprised between 5° and 40°.
More particularly, during each vibration, in a contact phase, pin 6 penetrates lever fork 8 with a depth of travel P greater than 100 micrometres, and in an unlocking phase, pin 6 remains at a distance from lever fork 8 with a safety distance S greater than 25 micrometres.
Fork 8 of lever 7 is thus enlarged compared to a conventional Swiss lever fork, which is much narrower and allows less freedom to pin 6, which would not be able to enter and exit the fork of a conventional Swiss lever with such a small angular amplitude. This concept of an enlarged fork allows a lever escapement to operate even when the resonator amplitude is much smaller than in a conventional balance spring, which is particularly advantageous for resonators with flexure bearings, which have a low amplitude, as in the current case. Indeed, it is important for the balance to be completely free at certain instants during the operating cycle.
Impulse pin 6 and lever fork 8 are advantageously dimensioned such that the width L of lever fork 8 is greater than (P+S)/sin(α/2+β/2), depth of travel P and safety distance S being measured radially with respect to main axis DP.
The useful width L1 of pin 6, seen in
Examination of the Figures reveals a complementary action on the positioning of pin 6, which is located much further from the axis of rotation of balance 2 than in a conventional escapement mechanism: the larger radius combined with a lower angle of pivoting makes it possible to maintain an equivalent curvilinear travel of pin 6, which is necessary for the pin to be able to perform its distribution/counting function. The use of a large-diameter balance is thus particularly advantageous.
More particularly, the eccentricity E2 of pin 6 with respect to the axis of the balance, and the eccentricity E7 of the horn of fork 8 with respect to the axis of lever 7, are comprised between 40% and 60% of the distance of centres E between the axis of lever 7 and the balance axis. More particularly, eccentricity E2 is comprised between 55% and 60% of distance of centres E, and eccentricity E7 is comprised between 40% and 45% of distance of centres E. More particularly, the area of interference between pin 6 and fork 8 extends over 5% to 10% of distance of centres E.
Thus, by design, the invention defines a new impulse pin/fork layout which has a very particular characteristic, wherein the horns of the fork are further apart, and the pin is wider than in a known type of Swiss lever mechanism with a normal angle of lift of 50°.
Thus, by substantially enlarging the lever fork in comparison to the usual proportions, it is also possible to design a Swiss lever escapement with a very small angle of lift, for example on the order of 10°.
Likewise,
Unlike a Swiss lever, whose pallets each have a dual function, namely stopping the escape wheel in a locked phase on a locking face, and imparting an impulse on an impulse face, the coaxial lever 7 of
Likewise, each escape wheel tooth for a Swiss lever escapement performs both the lock and impulse functions, which is certainly advantageously in terms of space. However, the Swiss lever is ill-suited to low-amplitude oscillations, which are a normal feature of resonators having flexure bearings, particularly with flexible strips. It is sought to ensure perfect operation of the escapement mechanism at low resonator amplitudes and with the best possible efficiency. For this reason, escape wheel set 4 is more complex here, as it includes at least two levels, since:
Lever 7 also includes two horns, first horn 81 and second horn 82, which define together an enlarged fork according to the invention, arranged to cooperate with impulse pin 6 which is dimensioned according to the invention.
Balance 2 includes a radial arm carrying an impulse-face 610, which is arranged to cooperate with direct-impulse teeth 41 of escape wheel set 4.
Direct-impulse teeth 41 and indirect-impulse teeth 43 of the illustrated variant are of very reduced radial extension in comparison to that of locking teeth 42, particularly between 20% and 35%; in the illustrated example, the radial extension of indirect-impulse teeth 43 is 25% of that of locking teeth 42, and the radial extension of direct-impulse teeth 41 is 31% of that of locking teeth 42, which is on the order of 49% of distance of centres E between axis DP of balance 2 and axis DS of lever 7.
The overall dimensions of the balance are, however, increased compared to a balance of a balance/balance spring for a Swiss lever, since it is advantageous to move pin 6 away from the axis of pivoting of the inertia mass. The external surface 60 of pin 6 is on a radius of 120% here with respect to the radial extensions of locking teeth 42, or, referring to distance of centres E between the balance axis and the lever axis, 59% of E.
As regards the lever, with reference to the same radial extension of locking teeth 42, the radial dimension of the end of locking faces 71 and 72 is 60% here, i.e. 30% of E, that of impulse face 73 is 95%, i.e. 47% of E, as is that of horns 81 and 82.
The distance of centres between axis D4 of escape wheel 4 and axis DS of lever 7 is 58% of E here, and the distance of centres between axis DP of balance 2 and axis D4 of escape wheel 4 is 89% of E.
Pushed by escape wheel 4, lever 7 leads, rotates in clockwise direction C until it reaches balance 2, through cooperation between second lever horn 82 with pin 6 on a second edge 62, thereby indirectly transmitting the impulse from escape wheel 4 to balance 2, via lever 7.
These kinematics are only made possible by the considerable enlargement of the lever fork between first horn 81 and second horn 82, and the adjustment of depth of travel P and safety distance S, which, together, ensure that it is possible for pin 6 to exit the lever fork.
It is noted that this design dispenses with the presence of a guard pin on lever 7, which allows the lever to be made on one level, for example from micromachinable, silicon or similar material, by a LIGA or MEMS or similar process. Indeed, first horn 81 rests here on pin 6 when balance 2 describes its supplementary arc, which prevents the lever from pivoting in the event of impact, which makes the presence of a guard pin and, a fortiori, a safety roller, unnecessary on balance 2, which can therefore also be made on one level.
The advantage, for maximising the efficiency of the resonator, of the particular relation set out above, which links the inertia of the inertia element and the inertia of the lever in a ratio of more than 10,000, is evident.
It is therefore particularly advantageous to have a lever which is both very small and very light, and a balance of large dimensions and high mass.
More particularly, lever 7 is made of silicon, which allows for a miniaturised and very precise embodiment, with a density of less than one third of that of steel. The fact that the lever is made of silicon decreases its inertia compared to a metal lever. Low inertia of the lever compared to the balance is crucial in order to obtain good efficiency with a low amplitude and high frequency, in the present case of resonators with flexure bearings.
When permitted by the range of the watch, the balance is advantageously made of a heavy metal or alloy, containing gold, platinum, tungsten, or similar, and may include inertia blocks of similar composition. Otherwise, the balance is made in a conventional manner from a copper-beryllium alloy CuBe2 or similar and ballasted with poising inertia blocks and/or adjustment inertia blocks made of nickel silver or another alloy.
More particularly, this lever 7 is on a single level of silicon, placed on an arbor made of metal or similar, such as ceramic or otherwise, pivoted with respect to plate 1.
More particularly, escape wheel set 4 is an escape wheel made from micromachinable material, especially silicon or suchlike.
More particularly, escape wheel set 4 is an escape wheel that is perforated to minimise its inertia with respect to its axis of pivoting DE.
More particularly, lever 7 is perforated to minimise its inertia IA with respect to secondary axis DS.
Preferably, lever 7 is symmetrical with respect to secondary axis DS, in order to avoid any unbalance, and to avoid unwanted torque in the event of linear impact, particularly in translation. An additional advantage is thus the great ease of assembly of this very small component, which can be handled by the operator performing the assembly from any side.
More particularly, the largest dimension of this at least one inertia element 2 is greater than half the largest dimension of plate 1.
More particularly, main axis DP, secondary axis DS and the axis of pivoting of escape wheel set 4 are arranged to be centred at a right angle, whose apex is on secondary axis DS. It is thus clear that, compared to a conventional T-shaped Swiss lever with a lever shaft and two arms, the shaft is removed and becomes one of the two arms 76, seen in
Comparison with the Swiss lever can be continued as regards the means for preventing overbanking, usually formed by a guard pin located on an offset plane of the lever. This function is important for preventing any jamming of the balance. In particular, the balance has no safety roller and thus no roller notch arranged to cooperate with such a guard pin. Here, because of the small angles of pivoting, the pin is never far from the fork. The overbanking prevention function is thus advantageously performed by the combination of edge 60, in the form of an arc of a circle, of pin 6, and by the corresponding surface 810, 820, of the horn 81, 82 concerned: this horn plays the usual part of a guard pin, and the periphery of the pin plays the part of the safety roller. The additional resulting advantage is that, where it cooperates with the single-level lever, the balance can also be on one level, which simplifies its fabrication and reduces its cost.
The design of a single-level lever, which greatly simplifies fabrication of the lever, is possible only because overbanking is thus prevented by the low amplitude of the resonator, combined with the large width of the pin (pin width is approximately equal to the enlarged fork).
More particularly, the flexure bearing includes two flexible strips 5 which are crossed in projection onto a plane perpendicular to main axis DP, at a virtual pivot defining main axis DP, and located on two parallel and distinct levels. More particularly still, the two flexible strips 5, in projection onto a plane perpendicular to main axis DP, form therebetween an angle comprised between 59.5° and 69.5°, and intersect at between 10.75% and 14.75% of their length, such that resonator mechanism 100 has a deliberate isochronism error which is the additive inverse of the loss error at the escapement of escapement mechanism 200.
The resonator thus has an anisochronism curve which compensates for the loss caused by the escapement. This means that the detached resonator is designed with an isochronism error which is the additive inverse of the error caused by the lever escapement. The design of the resonator therefore compensates for the loss at the escapement.
More particularly, the two flexible strips 5 are identical and are positioned in symmetry. More particularly still, each flexible strip 5 forms part of a one-piece assembly 50, in one piece with two solid parts 51, 55, and with its first means of alignment 52A, 52B, and of attachment 54 to plate 1, or, advantageously and as seen in
In the non-limiting variant illustrated in the Figures, the first alignment means are a first V-shaped portion 52A and a first flat portion 52B, and the first attachment means include at least a first bore 54. A first press strip 53 presses on the first attachment means. Likewise, one-piece assembly 50 includes, for attachment thereof to inertia element 2, second alignment means which are a second V-shaped portion 56A and a second flat portion 56B and the second attachment means include at least a second bore 58. A second press strip 57 presses on the second attachment means.
Flexure bearing 3 with crossed strips 5 is advantageously formed of two identical, silicon, one-piece assemblies 50, assembled in symmetry to form the crossing of the strips, and aligned precisely with respect to each other by means of the integrated alignment means and auxiliary means, such as pins and screws, which are not represented in the Figures.
Thus, more particularly, at least resonator mechanism 100 is attached to an intermediate elastic suspension strip 9 attached to plate 1 and arranged to allow a displacement of resonator mechanism 100 in the direction of main axis DP, and plate 1 includes at least one shock absorber stop 11, 12, at least in the direction of main axis DP, and preferably at least two such shock absorber stops 11, 12, which are arranged to cooperate with at least one stiff element of this at least one inertia element 2, for example a flange 21 or 22 added during assembly of the inertia element to flexure bearing 3 comprising strips 5.
The elastic suspension strip 9, or a similar device, allows displacements of the entire resonator 100 substantially in the direction defined by virtual axis of rotation DP of the bearing. The object of this device is to avoid strips 5 breaking in the event of transverse impact in direction DP.
More particularly, inertia element 2 includes inertia blocks 20 for adjusting rate and unbalance.
More particularly, pin 6 is in one-piece with a flexible strip 5, or more particularly, a one-piece assembly 50 as illustrated in the Figures.
More particularly, lever 7 includes bearing surfaces arranged to cooperate in abutment with teeth comprised in escape wheel set 4 and to limit the angular travel of lever 7. These bearing surfaces limit the angular travel of the lever, as solid banking would do. The angular travel of lever 78 can also be limited in a conventional manner by banking pins 700.
More particularly, flexure bearing 3 is made of oxidised silicon to compensate for the effects of temperature on the rate of regulating mechanism 300.
The invention also concerns a timepiece movement 500 comprising drive means 400, and such a regulating mechanism 300, whose escapement mechanism 200 is subjected to the torque of these drive means 400.
The graphs of
The invention also concerns a watch 1000, more particularly a mechanical watch, including such a movement 500, and/or such a regulating mechanism 300.
In short, the present invention makes it possible to increase the power reserve and precision of current mechanical watches. For a given movement size, the autonomy of the watch can be quadrupled, and the regulating power of the watch can be doubled. This means that the invention provides a gain of a factor 8 in the performance of the movement.
Those skilled in the art can advantageously refer to Thesis No. 3806 (2007) by M. Thierry CONUS, EPFL Lausanne (Switzerland) entitled, ‘Conception et optimisation multicritère des échappements libres pour montres-bracelet mécaniques’ (Multi-criteria design and optimisation of detached escapements for mechanical wristwatches), pages 107 to 141, including section 8.5.1 Bistable stop device and tangential impulse, pages 129 to 132.
The invention also concerns various very different escapement mechanisms, including, in a non-limiting manner, all detached escapements having a bistable stop device, including the following:
| Number | Date | Country | Kind |
|---|---|---|---|
| 16200152 | Nov 2016 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2017/080121 | 11/22/2017 | WO |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2018/095997 | 5/31/2018 | WO | A |
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| 20080219104 | Jurin | Sep 2008 | A1 |
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| Number | Date | Country |
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| 698 105 | May 2009 | CH |
| 2 894 520 | Jul 2015 | EP |
| 2 990 885 | Mar 2016 | EP |
| 3 032 352 | Jun 2016 | EP |
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| Number | Date | Country | |
|---|---|---|---|
| 20190243308 A1 | Aug 2019 | US |
