Rotating resonator with flexure bearing maintained by a detached lever escapement

Abstract

Timepiece regulator comprising a detached lever escapement mechanism, and a resonator with a quality factor Q including at least one inertia element including an integral impulse pin cooperating with a fork of the lever, this inertia element being subjected to the action of elastic return means directly or indirectly fixed to the plate and being arranged to cooperate indirectly with an escape wheel set comprised in the escapement mechanism, this resonator mechanism is a resonator with a virtual pivot rotating about a main axis (DP), with a flexure bearing subjected to the return force of at least two flexible strips attached to the plate, defining together a virtual pivot with a main axis (DP), the lever pivoting about a secondary axis (DS), and the fork is enlarged in comparison to the fork of a conventional Swiss lever.

Claims

1. A timepiece regulating mechanism, comprising, arranged on a main plate, a resonator mechanism with a quality factor Q, rotating about a main axis (DP), and an escapement mechanism which is subjected to the torque of drive means comprised in a movement, said resonator mechanism comprising at least one 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 attached to said plate, and said at least one inertia element being arranged to cooperate indirectly with an escape wheel set comprised in said escapement mechanism, wherein said elastic return means include at least two flexible strips to which is suspended said at least one inertia element and which define a flexure bearing with a virtual pivot for said at least one inertia element, said at least one inertia element carrying an integral pin, and said escapement mechanism includes a lever arranged to pivot about a secondary axis (DS) and including a lever fork arranged to cooperate with said impulse pin, and is a detached escapement mechanism, wherein, during the operating cycle, said resonator mechanism has at least one unlocking phase in which said impulse pin is at a distance from said lever fork, wherein, during each vibration, in a contact phase, said impulse pin penetrates said lever fork 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 of said at least one unlocking phase, said impulse pin remains at a distance from said lever fork with a safety distance (S) greater than or equal to 10 micrometres, and less than or equal to 60 micrometres, and said impulse pin and said lever fork are dimensioned such that the width (L) of said lever fork is greater than (P+S)/sin(α/2+P/2), said depth of travel (P) and said safety distance (S) being measured radially with respect to said main axis (DP), wherein α is the angle of lift of the lever which corresponds to the maximum angular travel of said lever fork, and wherein β is the angle of lift of the resonator, during which said impulse pin is in contact with said lever fork, and wherein the largest dimension of said at least one inertia element is greater than half the largest dimension of said plate.

2. The timepiece regulating mechanism according to claim 1, wherein said depth of travel (P) is greater than or equal to 80 micrometres and less than or equal to 120 micrometres.

3. The timepiece regulating mechanism according to claim 1, wherein said depth of travel (P) is greater than or equal to 100 micrometres.

4. The timepiece regulating mechanism according to claim 1, wherein said safety distance (S) is greater than or equal to 20 micrometres and less than or equal to 30 micrometres.

5. The timepiece regulating mechanism according to claim 1, wherein said safety distance (S) is greater than or equal to 25 micrometres.

6. The timepiece regulating mechanism according to claim 1, wherein said lift angle (α) of the lever is greater than or equal to 5° and less than or equal to 30°.

7. The timepiece regulating mechanism according to claim 6, wherein said lift angle (α) of the lever is less than or equal to 20°.

8. The timepiece regulating mechanism according to claim 7, wherein said lift angle (α) of the lever is greater than or equal to 12° and less than or equal to 16°.

9. The timepiece regulating mechanism according to claim 1, wherein said lift angle (β) of the resonator is greater than or equal to 3° and less than or equal to 30°.

10. The timepiece regulating mechanism according to claim 9, wherein said lift angle (β) of the resonator is greater than or equal to 8° and less than or equal to 12°.

11. The timepiece regulating mechanism according to claim 9, wherein said lift angle (β) of the resonator is less than or equal to 10°.

12. The timepiece regulating mechanism according to claim 1, wherein said lever forms a bistable stop device.

13. The timepiece regulating mechanism according to claim 1, wherein inertia IB of all of said inertia elements with respect to said main axis (DP), and inertia IA of said lever with respect to said secondary axis (DS), are such that the ratio IB/IA is greater than 2Q.Math.α.sup.2/(0.1.Math.π.Math.β.sup.2), where α is the lift angle of the lever which corresponds to the maximum angular travel of said lever fork.

14. The timepiece regulating mechanism according to claim 1, wherein said overall lift angle (β) of the resonator is less than twice an angle of amplitude by which said at least one inertia element deviates furthest, in only one direction of motion, from a rest position.

15. The timepiece regulating mechanism according to claim 1, wherein an angle of amplitude, by which said at least one inertia element deviates furthest from a rest position, is comprised between 5° and 40°.

16. The timepiece regulating mechanism according to claim 1, wherein said lever is in a single layer of silicon, placed on an arbor pivoted with respect to said plate.

17. The timepiece regulating mechanism according to claim 1, wherein said escape wheel set is a silicon escape wheel.

18. The timepiece regulating mechanism according to claim 1, wherein said escape wheel set is an escape wheel which is perforated to minimise its inertia with respect to its axis of pivoting.

19. The timepiece regulating mechanism according to claim 1, wherein said lever is perforated to minimise its said inertia (IA) with respect to said secondary axis (DS).

20. The timepiece regulating mechanism according to claim 1, wherein said lever is symmetrical with respect to said secondary axis (DS).

21. The timepiece regulating mechanism according to claim 1, wherein a first line extending from said main axis (DP) to said secondary axis (DS) and a second line extending from an axis of pivoting (DE) of said escape wheel set to said secondary axis (DS) form a right angle whose apex is on said secondary axis (DS).

22. The timepiece regulating mechanism according to claim 1, wherein said flexure bearing includes two flexible strips which are crossed in projection onto a plane perpendicular to said main axis (DP), at said virtual pivot defining said main axis (DP), and located in two parallel and distinct levels.

23. The timepiece regulating mechanism according to claim 22, wherein said two flexible strips, in projection onto a plane perpendicular to said main axis (DP), form therebetween an angle comprised between 59.5° and 69.5°, and intersect in the projection at between 10.75% and 14.75% of their length, such that said resonator mechanism has a deliberate isochronism error which is the additive inverse of the loss error at the escapement of said escapement mechanism.

24. The timepiece regulating mechanism according to claim 22, wherein said two flexible strips are identical and are positioned in symmetry.

25. The timepiece regulating mechanism according to claim 22, wherein each said flexible strip forms part of a one-piece assembly in one piece with means thereof for alignment and attachment to said plate or to an intermediate elastic suspension strip attached to said plate and arranged to allow a displacement of said flexure bearing and of said at least one inertia element in the direction of said main axis (DP).

26. The timepiece regulating mechanism according to claim 2, wherein at least said resonator mechanism is attached to an intermediate, elastic suspension strip attached to said plate and arranged to allow a displacement of said resonator mechanism in the direction of said main axis (DP), and said plate includes at least one shock absorber stop at least in the direction of said main axis (DP), arranged to cooperate with at least one stiff element of said at least one inertia element.

27. The timepiece regulating mechanism according to claim 1, wherein said at least one inertia element includes inertia blocks for adjusting rate and unbalance.

28. The timepiece regulating mechanism according to claim 1, wherein said impulse pin is in one-piece with a said flexible strip.

29. The timepiece regulating mechanism according to claim 1, wherein said lever includes bearing surfaces arranged to cooperate in abutment with teeth comprised in said escape wheel set and to limit the angular travel of said lever.

30. The timepiece regulating mechanism according to claim 1, wherein said flexure bearing is made of oxidised silicon to compensate for the effects of temperature on the rate of said regulating mechanism.

31. The timepiece regulating mechanism according to claim 1, wherein said escapement mechanism is a coaxial escapement mechanism.

32. The timepiece regulating mechanism according to claim 1, wherein said escapement mechanism is a Fasoldt escapement mechanism.

33. The timepiece regulating mechanism according to claim 1, wherein said escapement mechanism is hinged stop Grasshopper escapement mechanism.

34. The timepiece regulating movement including drive means and a regulating mechanism according to claim 1, wherein said escapement mechanism is subjected to the torque of said drive means.

35. A watch comprising: a movement including the timepiece regulating mechanism according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other features and advantages of the invention will appear upon reading the following detailed description, with reference to the annexed drawings, in which:

(2) FIG. 1 includes a double graph including, on the same abscissa, the ratio between the inertia of the inertia element of the resonator and the inertia of the lever, and which shows, on the ordinate, for a particular example mechanism, on the one hand, in the positive portion in the top graph, the rate of efficiency of the regulator in %, and in the negative portion in the bottom graph, the losing rate in seconds per day; these top and bottom graphs are drawn for a same given escapement geometry, with specific values of the quality factor, angle of lift of the lever and operating amplitude.

(3) FIG. 2 represents a schematic, partial and perspective view of a timepiece movement, with a plate carrying a regulating mechanism according to the invention, comprising a resonator having flexure bearings with two flexible strips arranged on two parallel levels and crossed in projection, secured to the plate by means of an elastic element, this resonator including an extensive inertia element, shaped like the letter omega, and whose central portion, carried by the two flexible strips, carries an impulse pin arranged to cooperate with a symmetrical lever, (whose pivoting on the plate by means of a metal arbor is not represented), which in turn cooperates with a conventional escape wheel.

(4) FIG. 3 represents a plan view of the regulating mechanism of FIG. 2, arranged on the plate of the movement.

(5) FIG. 4 represents a plan view of the detail of the regulating mechanism of FIG. 2.

(6) FIG. 5 represents a partially exploded perspective view of the regulating mechanism of FIG. 2.

(7) FIG. 6 represents a plan view of a detail of the area of cooperation between the impulse pin of the inertia element of the resonator, and the lever fork, represented in a stop position on a banking pin.

(8) FIG. 7 represents a plan view of the lever of the mechanism of FIG. 2, shaped like the horns of Watusi cattle.

(9) FIG. 8 represents a plan view of the flexure bearing of the mechanism of FIG. 2.

(10) FIG. 9 represents a plan view of a particular embodiment of one level of the flexure bearing of the mechanism of FIG. 2.

(11) FIG. 10 represents a side view of the regulating mechanism of FIG. 2.

(12) FIG. 11 represents, in perspective, a detail of the regulating mechanism of FIG. 2, showing the shock absorber stops on its plate.

(13) FIGS. 12 to 14 are graphs comprising, on the abscissa, the torque applied to the escape wheel set, and on the ordinate, respectively the amplitude measured in degrees in FIG. 12, the loss in seconds per day in FIG. 13, and the efficiency of the regulator in % in FIG. 14.

(14) FIG. 15 is a block diagram which represents a watch comprising a movement with drive means and a regulating mechanism according to the invention.

(15) FIGS. 16 to 19 represent plan views of the kinematic stages, already symbolised by FIG. 6, as regards the impulse pin, the lever fork of FIG. 7, and the escape wheel set formed here by a conventional escape wheel:

(16) FIG. 16: escape wheel locked on the entry pallet, supplementary arc of the resonator.

(17) FIG. 17: unlocking;

(18) FIG. 18: start of impulse;

(19) FIG. 19: locking of the escape wheel on the exit pallet, supplementary arc of the resonator, and safety function;

(20) FIGS. 20 to 24 represent plan views of the kinematic stages in an escapement mechanism with a small angle of lift, including an escape wheel set formed by an escape wheel with coaxial wheels including, on distinct levels, direct-impulse teeth for direct impulse on the balance, locking teeth arranged to cooperate with the locking faces of a lever, and indirect-impulse teeth arranged to cooperate with an impulse-face of the same lever, which also includes two horns defining an enlarged fork according to the invention arranged to cooperate with the impulse pin which is dimensioned according to the invention; said balance includes a radial arm carrying an impulse-face arranged to cooperate with the direct-impulse teeth of the escape wheel set.

(21) FIG. 20: unlocking from the exit pallet: locking of an escape wheel locking-tooth on the locking-face of the exit pallet, supplementary arc of the resonator in an anti-clockwise direction until the impulse pin is stopped on a first horn of the lever fork, rotation of the lever in a clockwise direction.

(22) FIG. 21: indirect impulse: rotation of the escape wheel released in an anticlockwise direction, banking of an indirect-impulse tooth of the escape wheel on the impulse-face of the lever, which rotates clockwise until the second horn of the lever fork cooperates with the impulse pin, thereby indirectly transmitting the impulse from the escape wheel set to the balance, via the lever.

(23) FIG. 22: locking on the entry pallet: an escape wheel locking-tooth is stopped on the locking face of the entry pallet, end of the supplementary arc of the balance in an anticlockwise direction.

(24) FIG. 23: unlocking from the entry pallet: reversal of the direction of rotation of the balance, which moves away in a clockwise direction, the impulse pin rests on the second horn of the lever fork and drives it anticlockwise, until unlocking occurs between the locking face of the entry pallet and the locking-tooth of the escape wheel, thereby allowing rotation of the escape wheel.

(25) FIG. 24: indirect impulse: an indirect-impulse tooth of the escape wheel is stopped on the impulse-face of the balance, allowing the balance to be directly driven by the escape wheel set.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(26) 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.

(27) 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.

(28) 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.

(29) 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.

(30) 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.

(31) More particularly, depth of travel P is greater than or equal to 80 micrometres and less than or equal to 120 micrometres.

(32) More particularly still, depth of travel P is greater than or equal to 100 micrometres.

(33) More particularly still, safety distance S is greater than or equal to 20 micrometres and less than or equal to 30 micrometres.

(34) More particularly still, safety distance S is greater than or equal to 25 micrometres.

(35) More particularly, the lift angle α of the lever is greater than or equal to 5° and less than or equal to 30°.

(36) More particularly still, the lift angle α of the lever is less than or equal to 20°.

(37) More particularly, the lift angle α of the lever is greater than or equal to 12° and less than or equal to 16°.

(38) More particularly, the lift angle β of the resonator is greater than or equal to 3° and less than or equal to 30°.

(39) More particularly, the lift angle β of the resonator is greater than or equal to 8° and less than or equal to 12°.

(40) More particularly still, the lift angle β of the resonator is less than or equal to 10°.

(41) More particularly, lever 7 forms a bistable stop device

(42) 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 FIG. 1, it is observed that, under the simulation conditions, there is a threshold of good efficiency, higher than 35%, and of low loss, less than 8 seconds per day, where the inertia of the inertia element, particularly of a balance, is 10000 times greater than the inertia of the lever.

(43) 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 I.sub.B of all the inertia elements 2 with respect to main axis DP, on the one hand, and the inertia I.sub.A of lever 7 with respect to secondary axis DS on the other hand, are such that the ratio I.sub.B/I.sub.A is greater than 2Q.Math.α.sup.2/(ε.Math.π.Math.β.sup.2), where α is the lift angle of the lever which corresponds to the maximum angular travel of lever fork 8.

(44) More particularly, if one wishes to limit dynamic losses to a factor c=10%, the inertia I.sub.B of this at least one inertia element 2 with respect to main axis DP on the one hand, and the inertia I.sub.A of lever 7 with respect to secondary axis DS on the other hand, are such that the ratio I.sub.B/I.sub.A is greater than 2Q.Math.α.sup.2/(0.1.Math.π.Math.β.sup.2), where α is the lift angle of the lever which corresponds to the maximum angular travel of lever fork 8.

(45) 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.

(46) More particularly, the angle of amplitude by which inertia element 2 deviates furthest from a rest position, is comprised between 5° and 40°.

(47) 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.

(48) 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.

(49) 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.

(50) The useful width L1 of pin 6, seen in FIG. 6, is slightly smaller than width L of lever fork 8, and, more particularly, less than or equal to 98% of L. This pin 6 is advantageously tapered behind its useful width surface L1, the pin can, in particular, have a prismatic shape of triangular cross-section as suggested in the Figure, or similar.

(51) 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.

(52) 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.

(53) 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°.

(54) 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°.

(55) FIG. 6 shows that, even with very low angles of pivoting, it is possible for pin 6 to enter fork 8 with a good depth of travel P, and exit therefrom with a sufficient safety distance S.

(56) FIGS. 16 to 19 illustrate the kinematics and show that suitable depths of travel P and safety distances S are obtained by this combined design, wherein pin 6 is very far away from the balance axis and lever 7 has a particular shape, especially with an enlarged fork.

(57) Likewise, FIGS. 20 to 24 illustrate the kinematics in another escapement mechanism 200 with a low angle of lift, which includes an escape wheel set 4 formed by an escape wheel with coaxial wheels (which may form a one-piece assembly in a particular embodiment) comprising, on distinct levels: direct-impulse teeth 41 for direct impulse on the balance, locking teeth 42 arranged to cooperate with locking faces 71 and 72 of a lever 7, and indirect-impulse teeth 43 arranged to cooperate with an impulse face 73 of the same lever 7.

(58) 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 FIGS. 20 to 24 separates the functions: locking faces 71 and 72 perform only the lock function; impulse face 73 performs only the impulse function.

(59) 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: locking teeth 42, which cooperate with locking faces 71 and 72 for the lock function, must, in the present particular and non-limiting design, pass underneath the balance, in particular underneath its impulse face 610, while the direct-impulse teeth 41 which cooperate with impulse face 610 for a direct impulse, must be coplanar with the latter; indirect-impulse teeth 43, which cooperate with impulse face 73 of the lever for an indirect impulse, are on a third level in the non-limiting embodiment illustrated by the Figures, but it is possible to envisage housing them on one of the aforementioned two levels, provided that a mechanism is devised to avoid any interference, in particular as regards the balance arm carrying impulse face 610.

(60) 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.

(61) 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.

(62) 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.

(63) 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.

(64) 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.

(65) 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.

(66) FIG. 20 shows the unlocking from the exit pallet: locking of a locking tooth 42 on escape wheel 4 which is stopped on locking face 72 of the exit pallet of lever 7, rotation through the supplementary arc of balance 2 in an anticlockwise direction A until pin 6 is stopped on a first lever horn 81 by a first edge 61, balance 2 pushes lever 7, rotation of lever 7 in a clockwise direction C unlocks the escape wheel from the exit pallet locking face 72.

(67) FIG. 21 shows the indirect impulse: rotation of escape wheel 4, released in anticlockwise direction E, stopping of an indirect-impulse tooth 43 of escape wheel 4 on impulse face 73 of lever 7.

(68) 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.

(69) FIG. 22 shows the locking on the entry pallet: a locking-tooth 42 of escape wheel 4 is stopped on entry-pallet locking face 71 of lever 7. Balance 2 continues and then finishes its supplementary arc in anticlockwise direction B; it can pass beside first lever horn 81 without interfering therewith during its travel.

(70) FIG. 23 shows the unlocking from the entry pallet: after the end of the supplementary arc of the balance, there is a reversal in the direction of rotation of balance 2, which moves away in clockwise direction B, pin 6 rests on second horn 82 of lever 7 and drives it in anticlockwise direction D, until unlocking occurs between the locking face 71 of the entry pallet of lever 7 and locking-tooth 42 of escape wheel 4, thereby allowing rotation of escape wheel 4.

(71) FIG. 24 shows the indirect impulse: a direct-impulse tooth 41 of escape wheel 4 is stopped on impulse face 610 of balance 2, allowing balance 2 to be directly driven by escape wheel 4. Lever 7 remains driven by its second horn 82, pushed by pin 6.

(72) 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.

(73) 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.

(74) 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.

(75) 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.

(76) 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.

(77) 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.

(78) 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.

(79) More particularly, escape wheel set 4 is an escape wheel made from micromachinable material, especially silicon or suchlike.

(80) 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.

(81) More particularly, lever 7 is perforated to minimise its inertia I.sub.A with respect to secondary axis DS.

(82) 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.

(83) FIG. 7 shows the two horns 81 and 82 arranged to cooperate with pin 6, pallets 72 and 73 arranged to cooperate with teeth of escape wheel set 4, and horn-like elements 80 and pallet-like elements 70 whose only role is to achieve perfect balancing.

(84) More particularly, the largest dimension of this at least one inertia element 2 is greater than half the largest dimension of plate 1.

(85) 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 FIG. 7, which carries horns 81 and 82 and exit pallet 72 almost coincident with horn 82, the other arm 75 carrying entry pallet 73.

(86) 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.

(87) 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).

(88) 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.

(89) 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.

(90) 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 FIG. 10, of attachment to an intermediate elastic suspension strip 9 attached to plate 1, and which is arranged to allow a displacement of the flexure bearing and this at least one inertia element 2 in the direction of main axis DP, so as to ensure good protection against shocks in direction Z perpendicular to the plane of such a one-piece assembly 50, and thus prevent breakage of the flexure bearing strips. This intermediate elastic suspension strip 9 is advantageously made of a Durimphy alloy or similar.

(91) 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.

(92) 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.

(93) 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.

(94) 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.

(95) FIG. 11 illustrates the presence of shock absorber stops limiting the travel of this at least one inertia element 2 in three directions in case of impact, but located at a sufficient distance for the inertia element not to touch the stops under the effect of gravity. For example, flange 21 or 22 includes a bore 211 and a face 212, able to cooperate respectively in a shock absorber stop arrangement with a trunnion 121 and a complementary surface 122 on stop 21 or 22.

(96) More particularly, inertia element 2 includes inertia blocks 20 for adjusting rate and unbalance.

(97) 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.

(98) 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.

(99) More particularly, flexure bearing 3 is made of oxidised silicon to compensate for the effects of temperature on the rate of regulating mechanism 300.

(100) 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.

(101) The graphs of FIGS. 12 to 14 set out a series of results from simulations in which Q=2000, I.sub.B=26550 mg.Math.mm.sup.2, the frequency is 20 Hz, the escape wheel set has 20 teeth, more particularly the lift angle α of the lever is 14°, and the lift angle β of the resonator is 10°.

(102) The invention also concerns a watch 1000, more particularly a mechanical watch, including such a movement 500, and/or such a regulating mechanism 300.

(103) 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.

(104) 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.

(105) 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: Swiss lever escapement Coaxial escapement Fasoldt escapement (page 130, Thesis by T. Conus) Grasshopper escapement (page 133, Thesis by T. Conus) Bourquin de la Heute escapement (page 119, Thesis by T. Conus) Daniel's escapement (page 123, Thesis by T. Conus) Breguet natural escapement (page 133, Thesis by T. Conus) Robin escapement Roskopf pin pallet escapement (page 121, Thesis by T. Conus) Melly escapement (page 130, Thesis by T. Conus) Daniels independent double wheel escapement (page 132, Thesis by T. Conus).