Rotating resonator with flexure bearing maintained by a detached lever escapement
11467537 · 2022-10-11
Assignee
Inventors
- Pascal Winkler (Saint-Blaise, CH)
- Jean-Luc Helfer (Le Landeron, CH)
- Gianni Di Domenico (Neuchatel, CH)
Cpc classification
G04B18/02
PHYSICS
G04B17/28
PHYSICS
G04B15/14
PHYSICS
International classification
G04B17/28
PHYSICS
G04B18/02
PHYSICS
Abstract
A timepiece regulator includes a detached lever escapement mechanism, and a resonator with a quality factor Q including an inertia element comprising an impulse pin integral with an inertia element and cooperating with a fork of the lever. This inertia element is subjected to the action of elastic return means directly or indirectly fixed to the plate and is 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).
Claims
1. A timepiece regulating mechanism, comprising, arranged on a main plate, a resonator mechanism, 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 attached to said plate, and said inertia element being arranged to cooperate indirectly with an escape wheel set comprised in said escapement mechanism, wherein said resonator mechanism is a resonator with a virtual pivot rotating about a main axis (DP), with a flexure bearing including at least two flexible strips, and including an impulse pin integral with said inertia element, wherein said escapement mechanism includes a lever pivoting 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 phase of freedom in which said impulse pin is at a distance from said lever fork, 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 said two flexible strips are located in two parallel and distinct levels, and the lift angle (β) of the resonator, during which said impulse pin is in contact with said lever fork, is less than 10°, and wherein said main axis (DP), said secondary axis (DS) and the axis of pivoting (DE) of said escape wheel set, are arranged to be centred at a right angle whose apex is on said secondary axis (DS) within a plane defined perpendicular to the main axis, the secondary axis, and the axis of pivoting.
2. The regulating mechanism according to claim 1, wherein the inertia IB of said inertia element with respect to said main axis (DP) on the one hand, and the inertia IA of said lever with respect to said secondary axis (DS) on the other hand, 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 a total angular travel of said lever fork from one side to the other and Q is a quality factor of the resonator mechanism.
3. The regulating mechanism according to claim 1, wherein said overall lift angle (β) of the resonator is less than twice the angle of amplitude by which said inertia element deviates furthest, in only one direction of motion, from a rest position.
4. The regulating mechanism according to claim 1, wherein the angle of amplitude, by which said inertia element deviates furthest from a rest position, is comprised between 5° and 40°.
5. The regulating mechanism according to claim 1, wherein, during each vibration, in a contact phase, said impulse pin penetrates said lever fork with a depth of travel (P) greater than 100 micrometres, and in an unlocking phase, said impulse pin remains at a distance from said lever fork with a safety distance (S) greater than 25 micrometres, and in that 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+β/2), where α is the lift angle of the lever which corresponds to a total angular travel of said lever fork from one side to the other, said depth of travel (P) and said safety distance (S) being measured radially with respect to said main axis (DP).
6. The 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.
7. The regulating mechanism according to claim 1, wherein said escape wheel set is a silicon escape wheel.
8. The 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.
9. The regulating mechanism according to claim 1, wherein said lever is perforated to minimise its said inertia (IA) with respect to said secondary axis (DS).
10. The regulating mechanism according to claim 1, wherein said lever is symmetrical with respect to said secondary axis (DS).
11. The regulating mechanism according to claim 1, wherein the largest dimension of said inertia element is greater than half the largest dimension of said plate.
12. The regulating mechanism according to claim 1, 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 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.
13. The regulating mechanism according to claim 1, wherein said two flexible strips are identical and are positioned in symmetry.
14. The regulating mechanism according to claim 1, 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 inertia element in the direction of said main axis (DP).
15. The regulating mechanism according to claim 1, 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 in that said plate includes at least one shock absorber stop at least in the direction of said main axis (DP), arranged to cooperate with a stiff element of said inertia element.
16. The regulating mechanism according to claim 1, wherein said inertia element includes inertia blocks for adjusting rate and unbalance.
17. The regulating mechanism according to claim 1, wherein said impulse pin is in one-piece with a said flexible strip.
18. The 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.
19. The 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.
20. A timepiece 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.
21. A watch including a regulating mechanism according to claim 1.
22. A timepiece regulating mechanism, comprising, arranged on a main plate, a resonator mechanism, 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 attached to said plate, and said inertia element being arranged to cooperate indirectly with an escape wheel set comprised in said escapement mechanism, wherein said resonator mechanism is a resonator with a virtual pivot rotating about a main axis (DP), with a flexure bearing including at least two flexible strips, and including an impulse pin integral with said inertia element, wherein said escapement mechanism includes a lever pivoting 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 phase of freedom in which said impulse pin is at a distance from said lever fork, 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 said two flexible strips are located in two parallel and distinct levels, and the lift angle (β) of the resonator, during which said impulse pin is in contact with said lever fork, is less than 10°, and wherein, during each vibration, in a contact phase, said impulse pin penetrates said lever fork with a depth of travel (P) greater than 100 micrometres, and in an unlocking phase, said impulse pin remains at a distance from said lever fork with a safety distance (S) greater than 25 micrometres, and in that 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+β/2), where α is the lift angle of the lever which corresponds to a total angular travel of said lever fork from one side to the other, said depth of travel (P) and said safety distance (S) being measured radially with respect to said main axis (DP).
23. A timepiece regulating mechanism, comprising, arranged on a main plate, a resonator mechanism, 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 attached to said plate, and said inertia element being arranged to cooperate indirectly with an escape wheel set comprised in said escapement mechanism, wherein said resonator mechanism is a resonator with a virtual pivot rotating about a main axis (DP), with a flexure bearing including at least two flexible strips, and including an impulse pin integral with said inertia element, wherein said escapement mechanism includes a lever pivoting 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 phase of freedom in which said impulse pin is at a distance from said lever fork, 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 said two flexible strips are located in two parallel and distinct levels, and the lift angle (β) of the resonator, during which said impulse pin is in contact with said lever fork, is less than 10°, and 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 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.
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:
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DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
(20) 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.
(21) 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 and an escapement mechanism 200, which is subjected to the torque of drive means 400, comprised in a movement 500.
(22) This resonator mechanism 100 includes an inertia element 2 which is arranged to oscillate with respect to plate 1. 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.
(23) According to the invention, resonator mechanism 100 is a resonator with a virtual pivot rotating about a main axis DP, with a flexure bearing including at least two flexible strips 5, and includes an impulse pin 6 integral with inertia element 2. Escapement mechanism 200 includes a lever 7, which pivots about a secondary axis DS and includes a lever fork 8 arranged to cooperate with impulse pin 6, and is thus a detached escapement mechanism: during its operating cycle, resonator mechanism 100 has at least one phase of freedom in which impulse pin 6 is at a distance from lever fork 8. The lift angle β of the resonator, during which impulse pin 6 is in contact with lever fork 8, is less than 10°.
(24) 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
(25) 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 E, 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/(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.
(26) More particularly, if one wishes to limit dynamic losses to a factor ε=10%, the inertia I.sub.B of 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.
(27) 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.
(28) More particularly, the angle of amplitude by which inertia element 2 deviates furthest from a rest position, is comprised between 5° and 40°.
(29) More particularly, during each vibration, in a contact phase, impulse pin 6 penetrates lever fork 8 with a depth of travel P greater than 100 micrometres, and in an unlocking phase, impulse pin 6 remains at a distance from lever fork 8 with a safety distance S greater than 25 micrometres.
(30) Fork 8 of lever 7 is thus enlarged compared to a conventional Swiss lever fork, which is much narrower, allowing 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.
(31) 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.
(32) The useful width L1 of impulse pin 6, seen in
(33) 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 impulse 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.
(34) 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.
(35) 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°.
(36) 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°.
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(39) 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.
(40) 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.
(41) 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.
(42) 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.
(43) 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.
(44) More particularly, escape wheel set 4 is a silicon escape wheel.
(45) 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.
(46) More particularly, lever 7 is perforated to minimise its inertia I.sub.A with respect to secondary axis DS.
(47) 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.
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(49) More particularly, the largest dimension of inertia element 2 is greater than half the largest dimension of plate 1.
(50) 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
(51) The 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 impulse 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 impulse 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 impulse 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.
(52) 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 impulse pin (pin width is approximately equal to the enlarged fork).
(53) 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.
(54) 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.
(55) 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
(56) 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.
(57) 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 inertia element 2, for example a flange 21 or 22 added during assembly of the inertia element to flexure bearing 3 comprising strips 5.
(58) 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.
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(60) More particularly, inertia element 2 includes inertia blocks 20 for adjusting rate and unbalance.
(61) More particularly, impulse pin 6 is in one-piece with a flexible strip 5, or more particularly, a one-piece assembly 50 as illustrated in the Figures.
(62) 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.
(63) More particularly, flexure bearing 3 is made of oxidised silicon to compensate for the effects of temperature on the rate of regulating mechanism 300.
(64) 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.
(65) The graphs of
(66) The invention also concerns a watch 1000, more particularly a mechanical watch, including such a movement 500, and/or such a regulating mechanism 300.
(67) 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.