Mechanical timepiece regulator

Abstract

The mechanical timepiece regulator of the invention comprises a flexure bearing oscillator and a double detent escapement, the oscillator comprising a balance wheel (1) connected to an elastic suspension (2a, 2b) arranged to guide and apply a restoring force to the balance wheel (1) in a plane of oscillation. The escapement comprises an escape wheel (3) and an anchor (4) integrated into the balance wheel (1) and having two arms (5, 6) arranged to receive alternately the impulses of the escape wheel (3). The escapement furthermore comprises two detents (7, 8) alternately locking the escape wheel (3) between two impulses and interacting with the arms (5, 6) of the anchor to release the escape wheel (3) before each impulse, without direct interaction between the anchor and the escape wheel.

Claims

1. Mechanical timepiece regulator comprising a flexure bearing oscillator and a double detent escapement, the oscillator comprising a balance wheel (1) connected kinematically to an elastic suspension (2a, 2b) arranged to guide and apply a restoring force to the balance wheel (1) in a plane of oscillation, the escapement comprising: an escape wheel (3), an anchor (4) integrated into the balance wheel (1) and having two arms (5, 6) arranged to receive alternately the impulses of the escape wheel (3), characterised in that said escapement furthermore comprises two detents (7, 8) alternately blocking the escape wheel (3) between two impulses and interacting with the arms (5, 6) of the anchor to release the escape wheel (3) before each impulse, without direct interaction between the anchor and the escape wheel.

2. Regulator according to claim 1, characterised in that each detent (7, 8) comprises a leaf spring one end of which is fixed (7a, 8a) and one end of which is free (7b, 8b), these free ends interacting both with an anchor arm (5, 6) and with the escape wheel (3).

3. Regulator according to claim 2, characterised in that the free end of each detent (7b, 8b) comprises a locking plane (7c, 8c) interacting with the teeth of the escape wheel (3) to lock it during the locking phase of the escapement while allowing the balance wheel (1) to oscillate without coming into contact with the escape wheel (3).

4. Regulator according to claim 2, characterised in that the free end of each detent (7, 8) comprises an unlocking plane 7d, 8d interacting with the anchor arms (5, 6) to release the escape wheel (3) before each impulse.

5. Regulator according to claim 1, characterised in that the ends of the anchor arms (5, 6) comprise impulse planes (5a, 6a) interacting with the teeth of the escape wheel (3) in such a way that energy is transferred from the escape wheel (3) to the balance wheel (1).

6. Regulator according to claim 5, characterised in that it comprises locking planes of detents (7c, 8c) arranged in relation to the anchor arms (5, 6) in such a way that at the end of the unlocking of one or the other of the detents, the tooth of the escape wheel (3) in contact with the locking plane of said detent transits directly on the impulse plane (5a, 6a) of the anchor arms (5, 6) without dropping.

7. Regulator according to claim 6, characterised in that the escape wheel (3) consists of only a single toothing realised on a single stage and works in the same plane P of operation as the impulse planes of the anchor (5a, 6a) and the locking planes of the detents (7c, 8c).

8. Regulator according to claim 5, characterised in that each of the two impulse planes (5a, 6a) receives one impulse from the escape wheel (3) for each period of the oscillator.

9. Regulator according to claim 5, characterised in that the impulse planes (5a, 6a) of the anchor arms have a curved shape.

10. Regulator according to claim 9, characterised in that the impulse planes (5a, 6a) of the anchor arms have a curved shape such that when the escape wheel (3) transfers its energy to the balance wheel, the escape wheel (3) moves with a uniform acceleration.

11. Regulator according to claim 1, characterised in that the regulator comprises a fixed base (9) comprising two rigid stops (10a, 10b) each respectively interacting with one of the detents (7, 8); each of these rigid stops is arranged to apply a pre-loading torque onto the respective detent.

12. Regulator according to claim 11 when it depends on any one of claims 2 to 4, characterised in that at least one of the detents (7, 8) comprises an end (8a) connected rigidly to an arm (13) interacting with a tuning table (11), this end (8a) being on the opposite end of said free end (7a, 8a) of said flexible detent (7, 8); the position of this tuning table (11) can be modified in relation to the fixed base (9) in order to change the orientation of the flexible detent (7, 8) in relation to its rigid stop (10a, 10b), thus changing the pre-loading torque of said flexible detent (7, 8) resting against the corresponding rigid stop (10a, 10b).

13. Mechanical timepiece regulator according to claim 1, characterised in that at least one of the detents (7, 8) interacts with a stiffening mechanism (14) arranged to change the active length of the leaf spring of said detent.

14. Regulator according to claim 1, characterised in that the anchor (4) comprises a tip (5b, 6b) on each of its arms (5, 6) interacting with a tooth of the escape wheel (3) in such a way that this tooth of the escape wheel (3) acts as a locking plane (3b) in the event that one of the detents (7, 8) does not manage to block the escape wheel (3).

15. Regulator according to claim 1, characterised in that the said elastic suspension (2a, 2b) comprises at least two leaf springs.

16. Regulator according to claim 15, characterised in that a first leaf spring (2a) of the said elastic suspension crosses a second leaf spring (2b) at the location of the centre of gravity of the balance wheel (1) and at 12.5% of the length of each leaf spring from the fixed base (9).

17. Regulator according to claim 1, characterised in that the balance wheel (1), the anchor (4) and the detents (7, 8) are made of silicon and the inertial body of the balance wheel (1a) is obtained by assembling a ring of dense material and a ring of silicon.

18. Timepiece movement comprising a regulator according to claim 1.

19. Wristwatch comprising a regulator according to claim 1.

Description

(1) The characteristics of the invention will become more apparent when reading the description of several embodiments solely given as examples, in no way limiting, and which refer to the schematic figures in which:

(2) FIG. 1 illustrates a front view of a regulator comprising a flexure bearing oscillator and a double detent escapement;

(3) FIG. 2 illustrates an oblique view of the same regulator;

(4) FIG. 3 illustrates an oblique view of the entry functions of the escapement;

(5) FIG. 4 illustrates an oblique view of the exit functions of the escapement;

(6) FIG. 5 illustrates a top view of the escapement in a locking position;

(7) FIG. 6 illustrates a top view of the escapement in an unlocking position;

(8) FIG. 7 illustrates a top view of the escapement in an impulse position;

(9) FIG. 8 illustrates a top view of the escapement at the end of an impulse phase;

(10) FIG. 9 illustrates a top view of the escapement in a locking position;

(11) FIG. 10 illustrates an alternative way of tuning the isochronism of the system.

(12) As illustrated in FIG. 1 and FIG. 2, the mechanical timepiece regulator comprises a flexure bearing oscillator and a double detent escapement, the oscillator comprising a balance wheel 1 connected kinematically to flexure blades 2a, 2b arranged to exert an elastic restoring force on the balance wheel 1 and guide it in a plane of oscillations. The escapement comprises an escape wheel 3 and an anchor 4 integrated into the balance wheel 1 and comprising two arms 5, 6 arranged to receive alternately the impulses of the escape wheel 3. The escapement furthermore comprises two detents 7, 8 blocking alternately the escape wheel 3 between two impulses and interacting with the arms 5, 6 of the anchor to release the escape wheel 3 before each impulse, without direct interaction between the anchor and the escape wheel.

(13) The flexure bearing oscillator comprises an inertial body 1a connected to the flexure blades 2a, 2b providing both the bearing function of the inertial body 1a in the desired trajectory and the elastic restoring force

(14) Each detent 7, 8 comprises a leaf spring one end of which is fixed 7a, 8a and one end of which is free 7b, 8b, this free end interacting both with an anchor arm 5, 6 and with the escape wheel 3.

(15) The isochronism error of the suspension 2a, 2b of the oscillator is corrected by the detents 7, 8. A single detent 7, 8 rests on the balance wheel 1 during the supplementary arc (arc described by a balance wheel outside the functions of the escapement) and the two detents 7, 8 are in contact with the balance wheel 1 during the unlocking phase of the escape wheel and the impulse. As the detents 7, 8 are flexible, the stiffness of the regulator varies during the oscillation. The detents 7, 8 therefore tend to decrease the average stiffness of the oscillator at high amplitudes. This compensates for the fact that the flexible suspension of the oscillator tends to be stiffer on average at high amplitudes.

(16) The free end of each detent 7b, 8b comprises a locking plane 7c, 8c (see FIGS. 2, 3 and 4) interacting with the teeth of the escape wheel 3 to block it during the locking phase of the escapement while allowing the balance wheel 1 to oscillate without coming into contact with the escape wheel 3.

(17) The free end of each detent 7, 8 comprises an unlocking plane interacting with the anchor arms 5, 6 to release the escape wheel 3 before each impulse.

(18) As illustrated in FIGS. 3 and 4, the ends of the anchor arms 5, 6 comprise impulse planes 5a, 6a interacting with the teeth of the escape wheel 3 in such a way that energy is transferred from the escape wheel 3 to the balance wheel 1. At the end of the first part of the impulse phase, the tip of the impulse plane 5c, 6c becomes the impulse beak and is pushed by the impulse plane of the tooth of the escape wheel 3c.

(19) The impulse planes 5a, 6a are preferably arranged contiguous with the locking planes of detents 7c, 8c to prevent a drop phase between the unlocking and impulse phases; otherwise, this drop phase would cause a loss of energy, therefore a lower efficiency of the escapement and therefore a lower amplitude of the balance wheel 1. This effect can be obtained by the fact that the escape wheel 3 only comprises a single toothing on a single stage and that the escape wheel 3 is located on the same plane P of operation as the locking planes 7c, 8c of the detents and the impulse planes of the anchor 5a, 6a.

(20) At each oscillation period of the oscillator, each of the two impulse planes 5a, 6a of the anchor arms receives an impulse from the escape wheel 3. These impulse planes 5a, 6a have a curved shape so that, when the escape wheel 3 transfers its energy to the balance wheel 1, the escape wheel 3 is essentially moving with a uniform acceleration. In other words, the impulse planes 5a, 6a are said to be “lightly touching”, in other words they guarantee at least a light touch of the tip of the escape wheel 3a on one of the impulse planes 5a, 6a during the impulse phase. This ensures continuous transfer of energy from the escape wheel 3 to the balance wheel 1. This characteristic is important for escapements interacting with a flexure bearing oscillator as the latter have the particular feature of having a high frequency, typically from 10 to 20 Hz, and a low amplitude, typically from 5 to 20 degrees. In this context, the impulse phase is brief and the balance wheel 1, for a given amplitude, sways fast. Furthermore, before the impulse the escape wheel 3 is stopped while the balance wheel 1 is close to its maximum velocity. Therefore, due to the “lightly-touching” impulse plane, the escape wheel 3 manages, in any case, to catch up with the balance wheel 1 and to transfer its energy to it whatever the amplitude of the balance wheel 1 (from zero to its nominal amplitude). Moreover, the “lightly-touching” profile of the impulse plane involves a variable gear ratio (ratio of rotation or rotational speed between two bodies) between the escape wheel 3 and the anchor 4. The torque applied to the anchor 4 is thus increased during the impulse so as to compensate for the increase of the elastic restoring torque of the elastic suspension 2a, 2b of the oscillator (like in every common spring the elastic torque increases when we stretch the spring). So even when the oscillator is stopped, the torque of the escape wheel 3 is sufficient to finish the impulse, which allows the system to be self-starting. The regulator comprises a fixed base 9 comprising two rigid stops 10a, 10b each respectively interacting with one of the detents 7, 8; each of these rigid stops is arranged to apply a pre-loading torque onto its respective detent.

(21) When the detents 7, 8 are not in contact with the balance wheel 1, they rest with a pre-loading torque on the rigid stops 10a, 10b. The pre-loading torque of at least one of the detents is adjustable and allows the isochronism error of the timepiece regulator to be tuned. Furthermore, the rigid stops 10a, 10b (see FIG. 7) and the pre-loading torque allow the detents 7, 8 to be precisely positioned during the locking phase of the escape wheel and to secure their positioning in case of external impacts.

(22) In the example illustrated by FIGS. 1 to 9, the orientation of the detent 8 is adjustable and allows the isochronism of the timepiece regulator to be adjusted. The detent 8 comprises one end 8a connected rigidly to an arm 13 interacting with a tuning table 11. This connected end 8a is on the opposite end of the free end 8b of the flexible detent 8; the position of this tuning table 11 can be modified in relation to the fixed base 9 in order to change the orientation of the flexible detent 8 in relation to its rigid stop 10b, thus changing the pre-loading torque of the flexible detent 8 resting against the corresponding rigid stop 10b. It is clear that this mechanism may also be used to make a fine tuning of the frequency of the system.

(23) Alternatively and illustrated in FIG. 10, still in order to adjust the isochronism or frequency of the system, the detent 8 may interact with a stiffening mechanism 14 arranged to modify the active length of the leaf spring of the detent.

(24) Coming back to the embodiment of FIGS. 1 to 9, each arm of the anchor 4 comprises a tip 5b, 6b interacting with a tooth of the escape wheel 3 in such a way that part 3b of this tooth of the escape wheel 3 acts as a locking plane in lieu of the detents 7, 8 in the event that, for example, following an impact, one of the latter cannot manage to block the escape wheel 3.

(25) Furthermore, it is also possible to add locking planes onto the balance wheel 1. These locking planes, for example, following an impact, would prevent one or the other of the detents from pivoting too much and release the escape wheel. These locking planes, therefore, would be involved only when the escape wheel 3 is at rest with said detent 7, 8.

(26) FIGS. 5 to 9 illustrate the sequential operation of the escapement with double detents during the semi-period of oscillation when the balance wheel 1 oscillates clockwise. The main phases of the escapement are the following: The escape wheel 3 starts by being at rest on the entry detent 7c (FIG. 5), the entry detent 7 is resting on its stop 10a and the exit detent 8 is resting on the exit arm 6 of the anchor. The pivoting of the balance wheel 1 causes the unlocking of the entry detent 7 by the entry arm of the anchor 5, which releases the escape wheel 3 (FIG. 6), the entry detent 7 is then no longer in contact with its stop 10a and is carried along by the entry arm of the anchor 5. The escape wheel 3 is now released and pivots clockwise (FIG. 7), the tip 3a of one of the teeth of the escape wheel is in contact with the lightly touching entry impulse plane 5a and pushes the anchor 4. The escape wheel 3 then continues its impulse (FIG. 8), the impulse plane 3c of the tooth pushing the entry arm of the anchor 5. At the end of the impulse, the opposite anchor arm leaves the detent on its stop. The entry impulse is completed (FIG. 9), the escape wheel 3 drops clockwise and is blocked by the locking plane 8c of the exit detent. The exit detent 8 is resting against its stop 10b and the entry detent 7 is carried along by the entry arm of the anchor 5.

(27) The following semi-period of oscillation then continues in an equivalent way with the rotation of the balance wheel 1 anti-clockwise followed by the unlocking, the impulse and the drop phases on the exit functions of the escapement.

(28) In the example illustrated, the elastic suspension 2a, 2b of the flexure bearing oscillator comprises two leaf springs, but it may comprise more and the topology chosen (here of type Wittrick according to EP2911012) to represent this oscillator is given solely by way of example and is in no way limiting.

(29) Owing to the regulator of the present invention, the energy consumption may be very low, less than 0.3 μW (typically 0.25 μW). Such a low power consumption is mainly associated with: the low amplitude of the balance wheel required to be isochronous and non-sensitive to gravity, typically between 8 and 16 degrees, the absence of friction in the flexible pivot of the balance wheel, the fact that the impulse is transferred directly from the escape wheel to the balance wheel which suppresses any loss of energy associated with an intermediate motion between the escape and balance wheels, the fact that the detents allow the friction that may occur to be limited during any locking or recoil phase, the absence of drop between the unlocking of the escape wheel and the impulse, and the minimisation of the escape wheel inertia.

(30) Another advantage of the present regulator is that the isochronism error of the double detent escapement naturally compensates for the isochronism error of the flexible pivot of the oscillator. This effect is obtained due to the fact that, unlike classical detent escapements, there is always at least one detent in contact with the balance wheel. Moreover, as explained previously, the isochronism error of the escapement of the present invention can be tuned, which allows to adapt to the isochronism of the oscillator that may vary from one oscillator to another due to imprecisions in the manufacturing and assembly of parts.

(31) Finally, the double detent escapement of the present regulator is self-starting because on the one hand there is an impulse every semi-period of oscillation unlike classical detent escapements and, on the other hand, no specific momentum is needed from the balance wheel to enable the unlocking of the escape wheel. Furthermore, the profile of the lightly touching impulse planes implies a variable gear ratio that increases the torque applied to the anchor by the escape wheel when the impulse finishes, which makes self-starting easier. (1) Balance wheel (1a) Inertial body (2a, 2b) Elastic suspension (3) Escape wheel (3a) Tip of a tooth of the escape wheel (3b) Safety locking plane of a tooth of the escape wheel (3c) Impulse plane of a tooth of the escape wheel (4) Anchor (5) Entry arm of the anchor (5a) Impulse plane of the entry arm of the anchor (5b) Safety tip of the entry arm of the anchor (5c) Impulse beak of the entry arm of the anchor (6) Exit arm of the anchor (6a) Impulse plane of the exit arm of the anchor (6b) Safety tip of the exit arm of the anchor (6c) Impulse beak of the exit arm of the anchor (7) Entry detent (7a) Fixed end of the entry detent (7b) Free end of the entry detent (7c) Locking plane of the entry detent (7d) Unlocking plane of the entry detent (8) Exit detent (8a) Fixed end of the exit detent (8b) Free end of the exit detent (8c) Locking plane of the exit detent (8d) Unlocking plane of the exit detent (9) Fixed base (10a) Stop of the entry detent (10b) Stop of the exit detent (11) Tuning table (12) Flexure bearing of the pre-loading tuning arm (13) Tuning arm (14) Stiffening means