OSCILLATOR OF A CLOCK WITH FLEXIBLE PEN

Description

[0001] The present invention relates to a flexible pivot oscillator intended to serve as a time base in a clockwork mechanism.

[0002] A flexible pivot oscillator is an oscillator whose oscillating member (balance wheel) is guided in rotation by an arrangement of elastic parts and not by a physical axis of rotation sliding in bearings. In addition to its rotational guidance function, the flexible pivot exerts a restoring torque on the oscillating member, similar to the balance spring of a sprung balance oscillator.

[0003] Unlike sprung balance oscillators, a flexible pivot oscillator does not produce dry friction during operation. It therefore has a better quality factor.

[0004] The present invention relates more particularly to a flexible pivot oscillator whose arrangement of elastic parts comprises blades extending in different parallel planes, typically so-called separate crossed blades which cross in top view without touching. Such watch oscillators are described for example in patent applications EP 2911012, EP 2998800, EP 3382470, EP 3839651, EP 3410229, EP 3502784, US 2020 / 0033804, WO 2016 / 096677, WO 2017 / 055983, WO 2018 / 109584 and WO 2022 / 009102.

[0005] An aim of the present invention is to improve the isochronism of such clock oscillators.

[0006] This object is achieved by a clock oscillator according to claim 1, particular embodiments being defined in the dependent claims.

[0007] The present invention further provides a watch regulating device and a timepiece comprising such a watch oscillator.

[0008] The invention will be better understood from reading the following detailed description given with reference to the appended drawings in which: there figure 1 is a perspective view of a clock oscillator according to the state of the art; figure 2 shows measurement results of the rate of the clock oscillator illustrated in figure 1 (graph G1) and a clock oscillator according to the invention (graph G2); the figures 3 et 4 are respectively a perspective view and a diametrical sectional view of a clock oscillator according to a first embodiment of the invention; figures 5 et 6 are respectively a perspective view and a diametrical sectional view of a clock oscillator according to a second embodiment of the invention; figures 7 et 8 are respectively a perspective view and a diametrical sectional view of a clock oscillator according to a third embodiment of the invention.

[0009] There figure 1 shows a watch oscillator 100 with separate crossed blades as described in patent application WO 2022 / 009102 of the present applicant. It comprises in particular a support 1, a balance 2, a flexible pivot 3 connecting the balance 2 to the support 1 and an impulse pin 4 secured to the balance 2.

[0010] The support 1 is intended to be mounted on a fixed or mobile frame of a watch mechanism. The flexible pivot 3 comprises first and second elastic blades 5, 6 which are identical but extend in parallel planes and in different directions to cross without contact. The crossing of the blades 5, 6 defines a virtual axis of rotation A of the balance 2 relative to the support 1, an axis of rotation which is perpendicular to said parallel planes and to the plane of the balance 2. The flexible pivot 3 thus serves to suspend the balance 2 from the support 1, to guide the balance 2 in rotation relative to the support 1 around the virtual axis of rotation A and to exert on the balance 2 an elastic restoring torque tending to bring it back into an equilibrium position relative to the support 1. The impulse pin 4 is intended to receive impulses from an escapement fork and to transmit them to the balance 2 to maintain the oscillations of the latter.

[0011] There figure 2 shows, by graph G1, an isochronism curve of oscillator 100. The ordinate is plotted for the rate in seconds per day and the abscissa is plotted for the oscillation amplitude of the balance in degrees. This graph G1 indicates more precisely the rate values ​​measured during oscillations of oscillator 100 maintained by a conventional escapement, in this case a Swiss lever escapement. As can be seen, a significant isochronism defect appears in a zone Z, namely a pronounced drop in the rate followed by a rapid rise. In the example illustrated, this defect occurs around an amplitude A 0 between 23° and 24°.

[0012] Such a defect significantly affects the accuracy of time measurement and may require operating the oscillator in an amplitude range separate from the Z zone. This defect can be explained by a resonance phenomenon due to the excitation of a parasitic pitch mode of the balance. In this parasitic mode, in addition to its oscillation in its plane around the A axis, the balance oscillates out of its plane around a Y axis that intersects the A axis perpendicularly.

[0013] To solve this problem, or at least mitigate it, it is proposed in the present invention to place the impulse pin adequately in order to avoid exciting the parasitic pitch mode. While in the oscillator 100 the impulse pin 4 is located at a different height from those of the balance 2 and the flexible pivot 3, the impulse pin in the present invention is arranged so that its functional zone, intended to be in contact with the escapement fork, crosses the plane of symmetry of the median planes of the blades 5, 6 perpendicular to the axis A. In this way, there is no longer, or almost no longer, a lever arm between the pitch axis Y and the interaction zone between the oscillator and the escapement and the resonance phenomenon mentioned above is eliminated or attenuated.

[0014] More precisely, the invention proposes a 100' clock oscillator (cf. figures 3 et 4 ) which differs from oscillator 100 in that the functional area of ​​the impulse pin 4' crosses the plane P3 of symmetry of the median plane P1, perpendicular to the axis A, of the blade 5 and the median plane P2, perpendicular to the axis A, of the blade 6.

[0015] Advantageously, the escapement fork 7, located at the same height as the functional zone of the impulse pin 4', is part of an anchor 8 and is raised relative to the body 9 of the anchor 8 to allow said body to extend in a plane different from that of the rim, 10, of the balance 2 and thus avoid any risk of collision between the anchor 8 and the balance 2 during operation of the oscillator.

[0016] The G2 graph of the figure 2 shows the rate measurement results obtained with the 100' oscillator. It can be seen that the isochronism defect mentioned above has disappeared, which makes it possible to choose an amplitude range for the operation of the oscillator independently of the parasitic frequencies.

[0017] The 100' oscillator as shown in figures 3 et 4 is formed of an assembly of stacked parts, namely a lower part 11, an upper part 12 and, between the two, the balance 2. The lower part 11 comprises a lower stage 13 of the support 1, the elastic blade 6 and a lower arm 14 connected to the lower stage 13 of the support 1 by the elastic blade 6. The upper part 12 comprises an upper stage 15 of the support 1, the elastic blade 5 and an upper arm 16 connected to the upper stage 15 of the support 1 by the elastic blade 5. In addition to the felloe 10, the balance 2 comprises a diametrical arm 17 interrupted in its central part so as not to interfere with the elastic blades 5, 6. This diametrical arm 17 is assembled to the lower and upper arms 14, 16 and serves as a spacer for the latter. Each of the lower and upper parts 11, 12 is monolithic and made for example of silicon, possibly coated with a layer, for example a layer of silicon oxide.The balance 2 is typically made of a dense material such as beryllium copper, gold, platinum, nickel silver or other dense metal or alloy. The lower and upper stages 13, 15 of the support 1 are superimposed while being separated by a spacer 18, for example metallic. The parts 2, 11, 12 and 18 are assembled by pins 19. A lower stop member 20 on the lower face of the lower arm 14, intended to cooperate in the event of impact with a stop fixed relative to the support 1 to protect the elastic blades 5, 6, carries the impulse pin 4' which extends parallel to the axis A. However, this impulse pin 4' could be carried by a member other than the lower stop member 20 and could be in another form.

[0018] THE figures 5 et 6 show a 100" clockwork oscillator according to a second embodiment of the invention. In this second embodiment, the impulse pin is replaced by a 4" impulse finger in one piece with the balance 2, therefore typically metallic, located in the same plane as the diametrical arm 17 and projecting radially from the two segments of the diametrical arm 17. The functional zone of the 4" impulse finger, intended to be in contact with the escapement fork 7, crosses the plane P3 of symmetry of the median planes P1 and P2 of the blades 5, 6 and is even centered with respect to this plane P3, as shown in figure 6 .

[0019] THE figures 7 et 8 illustrate a 100‴ clock oscillator according to a third embodiment of the invention. In this third embodiment, there is no spacer between the lower and upper parts 11, 12 and the balance 2 is located above the stack of the lower and upper arms 14, 16. A finger 4‴ formed by the superposition of two elementary fingers in a single piece with the lower and upper arms 14, 16 respectively and projecting radially from these arms constitutes the impulse element which cooperates with the escapement fork 7. Being defined by the lower and upper parts 11, 12, the impulse finger 4‴ is typically made of silicon, possibly coated with a layer, for example a layer of silicon oxide. The functional zone of the impulse finger 4'" crosses the plane P3 of symmetry of the median planes P1 and P2 of the blades 5, 6 and is even centered in relation to this plane P3, as visible on the figure 8 .

[0020] Although described in the context of a split cross-plate oscillator consisting of an assembly of stacked parts, the present invention applies equally well to single-piece split cross-plate oscillators, for example to the single-piece oscillator described in patent application EP 3502784.

[0021] The present invention applies more generally to any type of flexible pivot clock oscillator comprising elastic blades extending in different parallel planes. Other examples than separate crossed blades are non-coplanar RCC (Remote Center Compliance) blades.

[0022] The present invention is also not limited to two elastic blades. When the flexible pivot comprises more than two blades extending in different parallel planes, for example three or four blades, the functional zone of the impulse element crosses the plane of symmetry of all the median planes of the blades, this plane of symmetry being able to be one of the median planes of the blades (for example in the case of three blades) or a plane which separates one half of the blades from the other half of the blades (for example in the case of four blades). Examples of flexible pivots with multiple blades to which the invention can be applied are described in documents EP 2998800, EP 2911012, EP 3382470, EP 3410229 and US 2020 / 0033804.

[0023] The balance wheel 2 preferably has an annular rim 10, as shown in the figures 3 , 5 And 7, in order to maximize the inertia to mass ratio, but its rim could have any other desired shape, for example that of one or more segments, annular or not.

[0024] Furthermore, the escapement organ which cooperates with the impulse element 4', 4", 4‴ is not necessarily an anchor. It can be an escape wheel, in particular in the case of a direct impulse escapement, a lever or other.

[0025] The clock oscillator according to the invention can equip a timepiece such as a watch, in particular a wristwatch, or a clock.

Claims

1. Timepiece oscillator (100'; 100"; 100"') comprising a support (1), a balance (2) and a flexible pivot (3) to guide the balance (2) in rotation with respect to the support (1) about a virtual axis of rotation (A) and to exert a return force on the balance (2), the flexible pivot (3) comprising elastic strips (5, 6) having respective different middle planes (P1, P2) perpendicular to the virtual axis of rotation (A), the middle planes (P1, P2) as a whole being symmetrical with respect to a plane of symmetry (P3), the oscillator (100'; 100"; 100‴) further comprising an impulse element (4'; 4"; 4‴) fixed relative to the balance (2) and intended to cooperate with an escapement member (8), characterised in that the functional zone of the impulse element (4'; 4"; 4‴), intended to be in contact with the escapement member (8), crosses said plane of symmetry (P3).

2. Timepiece oscillator as claimed in claim 1, characterised in that said functional zone of the impulse element (4", 4‴) is centred with respect to said plane of symmetry (P3).

3. Timepiece oscillator as claimed in claim 1 or 2, characterised in that the balance (2) comprises an annular felloe (10).

4. Timepiece oscillator as claimed in any one of claims 1 to 3, characterised in that the impulse element (4') is a pin extending in parallel with the virtual axis of rotation (A).

5. Timepiece oscillator as claimed in any one of claims 1 to 3, characterised in that the impulse element (4"; 4‴) is a finger extending radially with respect to the virtual axis of rotation (A).

6. Timepiece oscillator as claimed in any one of claims 1 to 5, characterised in that said elastic strips (5, 6) comprise crossing first and second elastic strips.

7. Timepiece oscillator as claimed in any one of claims 1 to 6, characterised in that the flexible pivot (3) consists of two crossing elastic strips (5, 6).

8. Timepiece regulator device comprising a timepiece oscillator (100'; 100"; 100‴) as claimed in any one of claims 1 to 7 and an escapement member (8) cooperating with said functional zone of the impulse element (4'; 4"; 4‴).

9. Timepiece regulator device as claimed in claim 8, characterised in that the escapement member (8) comprises an escapement fork (7) cooperating with said functional zone of the impulse element (4'; 4"; 4‴).

10. Timepiece regulator device as claimed in claim 9, characterised in that the escapement member (8) is an anchor comprising a body (9) and the escapement fork (7), and in that the escapement fork (7) is raised with respect to the body (9).

11. Timepiece, for example a watch or miniature clock, comprising a timepiece oscillator as claimed in any one of claims 1 to 7 or a timepiece regulator device as claimed in any one of claims 8 to 10.