This application claims priority to European Patent Application No. 18169741.8 filed on Apr. 27, 2018, the entire disclosure of which is hereby incorporated herein by reference.
The invention concerns a timepiece resonator mechanism, comprising a structure and at least one inertia element arranged to oscillate in a pivoting motion about a pivot axis, with the centre of inertia of this at least one inertia element aligned on the pivot axis, this at least one inertia element being subjected to return forces exerted by at least one RCC flexure pivot comprising a plurality of elastic resonator strips, each directly or indirectly fixed at a first end to the structure and directly or indirectly fixed at a second end to said at least one inertia element, each elastic resonator strip extending in a plane perpendicular to the pivot axis, and being essentially deformable in the plane perpendicular to the pivot axis, wherein the elastic resonator strips are straight and extend in planes that are parallel to each other or coincident, and wherein the crossing, in projection onto a plane perpendicular to the pivot axis, of the directions in which the elastic resonator strips extend, defines the pivot axis.
The invention also concerns an oscillator including at least one such resonator mechanism and an escapement mechanism.
The invention also concerns a timepiece movement including at least one such oscillator and/or one at least one such resonator mechanism.
The invention also concerns a watch including such a timepiece movement and/or at least one such oscillator and/or at least one such resonator mechanism.
The invention concerns the field of timepiece resonators and more particularly those that include elastic resonator strips acting as return means for operation of the oscillator.
Shock resistance is a difficult issue for most timepiece oscillators, and in particular for crossed strip resonators. Indeed, during out-of-plane impact, the stress experienced by the strips rapidly reaches very high values, which, accordingly, reduces the travel that the part can make before yielding.
Shock absorbers for timepieces are available in many variants. However, their function, essentially, is to protect the fragile pivots of the arbor, and not the elastic elements, such as, conventionally, the balance spring.
European Patent Application No. EPEP3054357A1 in the name of ETA Manufacture Horlogère Suisse discloses a timepiece oscillator including a structure and distinct primary resonators, which are temporally and geometrically offset, each comprising a weight returned towards the structure by an elastic return means. This oscillator includes coupling means for the interaction between the primary resonators, including driving means for driving motion of a wheel set which includes driving and guiding means arranged to drive and guide a control means articulated to transmission means, each articulated, at a distance from the control means, to a weight of a primary resonator. The primary resonators and wheel set are arranged such that the articulation axes of any two primary resonators and the articulation axis of the control means are never coplanar.
European Patent Application EP3035127A1 in the name of SWATCH GROUP RESEARCH & DEVELOPMENT Ltd discloses a timepiece oscillator comprising a resonator formed by a tuning fork, which includes at least two mobile oscillating parts, fixed to a connection element by flexible elements whose geometry determines a virtual pivot axis of determined position with respect to a plate, and about which oscillates the respective mobile part, whose centre of mass coincides in the rest position with the respective virtual pivot axis.
For at least one moving part, the flexible elements are formed of crossed elastic strips at a distance from each other in two parallel planes, and whose directions, in projection onto one of the parallel planes, intersect at said virtual pivot axis of the moving part.
Swiss Patent Application No CH711573A2 in the name of PATEK PHILIPPE discloses a timepiece movement comprising a frame and a mechanism mounted in or on the frame, the mechanism comprising a flexure bearing system comprising a securing part and a moving part connected by elastic bearing parts. The flexure bearing system is located at least partly in an aperture of a frame element and is fixed by the securing part to the lateral wall of said aperture.
European Patent Application No. EP3021174A1 in the name of LVMH discloses a monolithic timepiece regulator made in a single plate, including a stiff external element, a stiff internal element, and elastic suspension members connecting the stiff external element to the stiff internal element and allowing oscillating rotational movements therebetween. The stiff internal element has arms which are rigidly connected to one another, leaving angular spaces free therebetween and the suspension members are situated in these free angular spaces.
The invention proposes to protect the strips of a strip resonator with RCC (remote centre of compliance) flexure pivots and thus to ensure better performance of the system.
To this end, the invention concerns a strip resonator mechanism according to claim 1.
The invention also concerns an oscillator including at least one such resonator mechanism and an escapement mechanism.
The invention also concerns a timepiece movement including at least one such oscillator and/or one at least one such resonator mechanism.
The invention also concerns a watch including such a timepiece movement and/or at least one such oscillator and/or at least one such resonator mechanism.
Other features and advantages of the invention will appear upon reading the following detailed description, with reference to the annexed drawings, in which:
The invention proposes to protect the strips of a strip resonator with RCC (remote centre of compliance) flexure pivots and thus to ensure better performance of the system.
Swiss Patent Application No. CH01511/16 in the name of Swatch Group Research & Development Ltd discloses anti shock devices for head-to-tail V-shaped flexure pivots and for RCC flexure pivots. This Application requires numerous banking arrangements which are advantageous for such mechanisms, easy to implement for those skilled in the art in combination with the disclosure of the present description, and which are not set out in detail again here.
It is to be noted that a head-to-tail V-shaped pivot arrangement has the advantage of juxtaposing four strips, at least one of which can bend or buckle to prevent breakage of the assembly.
The situation is more difficult for an impact occurring on an RCC pivot, since, if the direction of impact is parallel to one of the strips and tends to elongate the strip which is very stiff, the latter may break in the event of excessive elongation. The invention therefore proposes to provide a simple solution to this particular case.
To this end, the invention consists in introducing at least one anti shock element between the strips of the RCC pivot and the inertia element.
Thus, the invention concerns a timepiece resonator mechanism 100, comprising a structure 1 and at least one inertia element 2, which is arranged to oscillate in a pivoting motion about a pivot axis D. The centre of inertia of this at least one inertia element 2 is aligned on pivot axis D during oscillation.
This at least one inertia element 2 is subjected to return forces exerted by at least one RCC flexure pivot referenced 200 in
According to the invention, resonator mechanism 100 includes an anti-shock element 10, which includes a stiff element 13, on which are fixed the second ends of strips 3 and which is integral with at least one anti-shock strip 11 arranged to keep inertia element 2 suspended. This anti-shock element 10 provides shock protection for strips 3 of flexure pivot 200, 201, 301.
This stiff element 13 includes a chamber 16, which is delimited by an inner surface 15, to which is secured inside chamber 16 at least one such anti-shock flexible strip 11 arranged to keep an inner ring 14 suspended. This inner ring 14, thus suspended in stiff element 13, carries inertia element 2, or carries an arbor 22 comprised in inertia element 2.
The arrangement of the at least one anti-shock flexible strip 11, particularly a plurality of anti-shock flexible strips 11 as seen in
The fact that inner ring 14 is prevented from rotating ensures that anti-shock flexible strips 11 cannot disrupt operation of resonator mechanism 100.
The radial or paraxial travel of inner ring 14 can go to the stop position in contact with inner surface 15 of chamber 16 when the arrangement of anti-shock flexible strips 11 allows direct contact; if the arrangement of anti-shock flexible strips 11 does not allow direct contact between inner ring 14 and inner surface 15, as in the particular and non-limiting variant of
More particularly, stiff element 13 is at least 100 times stiffer, in every degree of freedom, than elastic resonator strips 3 of the flexure pivot, and than each anti-shock flexible strip 11 comprised in anti-shock elastic element 10.
Different arrangements of anti-shock flexible strips 11 are possible.
In a first variant, at least one anti-shock flexible strip 11 and more particularly each anti-shock flexible strip 11 is substantially coiled around pivot axis D.
In a second variant, each anti-shock flexible strip 11 is substantially of revolution around pivot axis D.
More particularly, anti-shock element 10 includes a plurality of identical anti-shock flexible strips 11, regularly distributed around pivot axis D.
In an advantageous embodiment seen in
Advantageously, anti-shock flexible strips 11 are calculated such that the rotational resonance frequency of anti-shock element 10 in its first natural mode is higher than 1000 Hz, or than several thousand Hz.
On the flexure pivot side, the oscillation frequency of inertia element 2 is more particularly comprised between 5 Hz and 100 Hz.
An assembly with two RCC pivots placed face-to-face makes it possible to:
cancel out the effects of position, during wear, on the resonator frequency; the centre of mass of the inertia weight must be equidistant from the RCC pivots;
stiffen the system and limit the movements of the inertia weight to rotation along the Z axis which corresponds to pivot axis D.
Thus, this at least one inertia element 2 is subjected to return forces exerted by a pair of identical RCC flexure pivots 201, 301, mounted face-to-face, and wherein all of strips 3 are fixed at their second end to a single, common anti-shock element 10.
The centre of mass of the inertia element is equidistant from the pivot axes of RCC flexure pivots 201, 301 when these axes are distinct, or aligned therewith when they are coaxial.
In a variant, in anti-shock element 10, at least one anti-shock flexible strip 11 is arranged to hold and elastically clamp inertia element 2. More particularly, anti-shock element 10 includes a plurality of anti-shock flexible strips 11, each arranged to hold and elastically clamp inertia element 2.
It can be said that, for the same inertia weight:
the rotational stiffness (resonance frequency of the system) of strips 11 is at least 100 times and more particularly at least 500 times, and more particularly still at least 1000 times greater than the stiffness of strips 3, in order not to disturb the resonance frequency;
the translational stiffness (resonance frequency of the system) in the plane of strips 11 is at least 100 times and more particularly at least 500 times, and more particularly still at least 1000 times lower than the stiffness of strips 3, in order to ensure movement in case of impact.
As regards the translational stiffness in direction Z of strips 11 and of strips 3, said stiffness is such that, in case of impact, both strips 11 and strips 3 participate in displacement of the inertia weight to the stop position.
More particularly, resonator mechanism 100 includes axial stop means comprising at least one lower axial stop and/or one upper axial stop, the axial stop means being arranged to abuttingly engage with at least one inertia element 2 in order to protect resonator mechanism 100 against axial impacts in the direction of pivot axis D.
The various arrangements of Swiss Patent Application No. CH01511/16 can advantageously be incorporated in this mechanism.
In a variant that is not illustrated, resonator mechanism 100 includes a plurality of such inertia elements 2 which extend over several parallel levels and resonator mechanism 100 includes at least one intermediate axial stop arranged between two adjacent levels of inertia elements 2.
The invention also concerns an oscillator 400 including such a resonator mechanism 100, arranged to cooperate with an escapement mechanism 300.
The invention also concerns a timepiece movement 500 including at least one such oscillator 400 and/or at least one such resonator mechanism 100.
The invention also concerns a watch 1000 including at least one such movement 500, and/or at least one such oscillator 400, and/or at least one such resonator mechanism 100.
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