BALANCE-SPRING FOR A HOROLOGICAL RESONATOR MECHANISM PROVIDED WITH MEANS FOR ADJUSTING FLEXIBILITY AND ASSOCIATED MATERIALS

Abstract

A balance-spring, in particular for a horological resonator mechanism, the balance-spring including a flexible strip coiled on itself into several coils, the strip having a predefined flexibility, the balance-spring including a device for adjusting its flexibility, the adjustment device including an elastic element in direct contact with the strip, the elastic element preferably having a flexibility less than that of the strip, the adjustment device including a prestressing device to apply a variable force or torque to the elastic element, so as to vary the flexibility of the elastic element, the elastic element and the strip being separate and assembled with each other. An horological resonator mechanism including such a balance-spring is also disclosed.

Claims

1. A balance-spring for a horological resonator mechanism, the balance-spring comprising a flexible strip coiled on itself into several coils, the strip having a predefined flexibility, the balance-spring including adjustment means for adjusting its flexibility, the adjustment means including an elastic element arranged in series with the strip, the elastic element connecting one end of said strip to a fixed support, so as to add an additional flexibility to the strip, the elastic element preferably having a flexibility less than that of the strip, the adjustment means including prestressing means to apply a variable force or torque to the elastic element, preferably without substantially modifying the position of the end of the strip, so as to vary only the flexibility of the elastic element, characterised in that wherein the elastic element and the strip are separate and assembled with each other by assembly means.

2. The balance-spring according to claim 1, wherein the elastic element is formed from a first material withstanding assembly processes generating stress induced in the first material, such as driving or screwing.

3. The balance-spring according to claim 2, wherein the prestressing means are formed from the first material.

4. The balance-spring according to claim 2, wherein the first material is to be chosen from metals or metal alloys, such as nickel-silver, CuBe2, steel or nickel-based alloys (Ni, NiP, NiW), or materials for LIGA type processes, such as alloys based on Ni, based on Co, based on CuNiSn, or a maraging type steel.

5. The balance-spring according to claim 2, wherein the strip is formed from a second material different from the first material, for example including silicon or silicon oxide.

6. The balance-spring according to claim 1, wherein the first and the elastic element are assembled by gluing as assembly means.

7. The balance-spring according to claim 1, wherein the elastic element is arranged at an outer end of the strip.

8. The balance-spring according to claim 1, wherein the elastic element comprises a flexible guide provided with at least one flexible blade, and with a movable rigid part to which the strip is connected.

9. The balance-spring according to claim 1, wherein the torque or force is continuously adjustable by the prestressing means.

10. The balance-spring according to claim 1, wherein the prestressing means comprise a secondary flexible blade connected to the elastic element.

11. The balance-spring according to claim 1, wherein the prestressing means comprise a lever to adjust the variable force or torque.

12. A rotary resonator mechanism for a horological movement, including an oscillating mass, wherein the mechanism comprises a balance-spring according to claim 1.

13. A horological movement, including a plate and a resonator mechanism according to claim 12, wherein the elastic element is assembled with at least one balance-spring stud.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0039] The aims, advantages and features of the present invention will become apparent upon reading several embodiments given only as non-limiting examples, with reference to the appended drawings wherein:

[0040] FIG. 1 schematically represents a perspective view of a part of a regulating organ comprising a balance-spring according to an embodiment of the invention, the regulating organ being arranged in a horological movement, and

[0041] FIG. 2 schematically represents a top view of the balance-spring of the regulating organ of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

[0042] FIG. 1 shows a schematic representation of an embodiment of a resonator mechanism or regulating organ 1 arranged in a horological movement 10. The horological movement 10 comprises a plate 21, an inertia-block, an elastic return element of the inertia-block configured to oscillate it, and a balance cock 22.

[0043] The regulating organ 1 further comprises an annular balance 23 as inertia-block, a balance shaft 24 and a balance-spring 25 as elastic return element.

[0044] The plate 21 is provided with a housing 26 to receive the regulating organ 1, wherein the balance 23, the balance-spring 25, the balance cock 22 are superposed from the bottom up. The balance shaft 24 is centred in the housing 26 and passes through the centre of the balance 22, the balance-spring 25 and the balance cock 22. The balance shaft 24 is held by two shockproof bearings 28 arranged at both ends of the balance shaft 24. A first bearing is arranged at the bottom of the housing 26, and the second bearing 28 is arranged on top of the housing 26, and is held by the balance cock 22, the balance cock 22 passing through the top of the housing 26 via the central axis of the housing 26. The balance cock 22 is provided with a through hole wherein the second bearing 28 is held.

[0045] Represented in FIGS. 1 and 2, the balance-spring 25 extends preferably substantially in one plane. The balance-spring 25 comprises a flexible strip 2 coiled on itself into several coils, the strip 2 having a predefined flexibility. The inner end 9 of the strip 2 is integral or assembled with a support 3. The support 3 has a substantially triangular shape, and is threaded around the shaft of the balance 23.

[0046] The balance-spring 25 further includes means for adjusting its flexibility. For example, the adjustment means can in particular be actuated by a user when the regulating organ is mounted on a plate of the horological movement.

[0047] The adjustment means include an elastic element 5 arranged in series with the strip 2, the elastic element 5 connecting one end 4, 9 of said strip 2 to a fixed support 17, and secured to one of the ends 4, 9 of the strip 2. The elastic element 5 is secured to the outer end 4 of the strip 2. The inner end 9 of the strip 2 is assembled with a support 3 of an oscillating mass of the resonator. The elastic element 5 is a different element from the strip 2. The fixed support 17 is fixed relative to the plate 21.

[0048] The elastic element 5 adds additional flexibility to that of the strip 2. Preferably, the elastic element 5 has a flexibility less than that of the strip 2. The elastic element 5 is here arranged in line with the strip 2.

[0049] The elastic element 5 of the balance-spring 25 comprises a flexible-blade guide comprising at least one flexible blade. The guide comprises here two uncrossed flexible blades 11, 12 and a rigid part 18. The flexible blades 11, 12 are joined, on one hand, laterally to a fixed support 17, and, on the other, to the rigid part 18 moving them closer together. Thus, preferably, the flexible blades 11, 12 move apart from the rigid part 18 to the fixed support 17. The outer end 4 of the strip 2 is joined to the rigid part 18. The fixed support 17 is stationary relative to the movement 10. The fixed support 17 has an L shape, a first arm 46 of the L serving as a link with the flexible blades 11, 12, the second arm 47 of the L being oriented on the opposite side to the uncrossed-strip guide to be able to be assembled with the horological movement 10.

[0050] The adjustment means of the balance-spring 25 further include prestressing means 6 to apply a variable force or torque to the elastic element 5. Thus, the flexibility of the balance-spring can be adjusted. The torque or force is continuously adjustable by the prestressing means 6. In other words, the torque or force is not restricted to isolated values. Thus, it is possible to adjust the flexibility of the elastic element 5 with high precision.

[0051] The prestressing means 6 include a secondary flexible strip 19, arranged on an opposite side of the rigid part 18 in line with the uncrossed-strip guide. The secondary flexible strip 19 is disposed tangentially to the strip 2, at the outer end 4.

[0052] The secondary flexible strip 19 is connected by the other end to a curved lever 14 partially bypassing the strip 2. The lever 14 is connected, in addition to the secondary flexible blade 19, to a semi-rigid structure 27 connected to the fixed support 17. The semi-rigid structure 27 is partially distorted when the lever 14 is actuated by the force or torque.

[0053] The force or torque is exerted on the free end 32 of the lever 14. Thus, the lever 14 of the prestressing means 6 transmits the variable force or torque to the elastic element 5 via the secondary flexible strip 19 and the semi-rigid structure 27, so as to modify the flexibility of the balance-spring 25.

[0054] According to the invention, the elastic element 5 and the strip 2 are separate, and are assembled with each other by assembly means. The assembly means are for example glue.

[0055] Preferably, the elastic element 5 is formed from a first material withstanding assembly processes generating stress induced in the first material, such as driving or screwing.

[0056] Driving is a process wherein a first piece is at least partially force-fitted in a housing of a second piece, and is held by friction in the housing. In other words, the housing clamps the part of the first piece.

[0057] Screwing is a process wherein two pieces are kept assembled thanks to a screw, which partially passes through the first and second piece to hold them together.

[0058] The first material is preferably to be chosen from metals or metal alloys, such as nickel-silver, CuBe2, steel, nickel or nickel-based alloys, for example nickel phosphorus NiP or nickel-tungsten NiW, or materials for LIGA type processes, such as alloys based on Ni, based on Co, based on CuNiSn, or a maraging type steel. An example of cobalt-based spring allow is phynox?, a maraging steel is Durnico?, and a CuNiSn alloy is ToughMet?.

[0059] Such materials can withstand stress induced by assembly processes, such as driving or screwing.

[0060] Preferably, the flexible strip 2 is formed from a second material different from the first material.

[0061] Preferably, the strip 2 is one-piece, and possibly formed from the same material. For example, the second material includes mostly silicon or silicon oxide, preferably entirely. Thus, the flexible strip 2 has the amagnetic properties of silicon. Alternatively, the second material is of Nivarox CT? type or of Nivachron? type, which are well-known to a person skilled in the art of watchmaking.

[0062] In a particular example, the prestressing means 6 are also formed from the first material. Thus, the prestressing means 6 and the elastic element 5 are more resistant and can be assembled with processes such as driving or screwing.

[0063] These assembly means withstand the force or torque produced by the prestressing means 6 better.

[0064] The same applies with the free end 15 of the lever 14, which cooperates with the first balance-spring stud 34. The first balance-spring stud includes a housing making it possible to press the free end therein.

[0065] The strip 2 and the elastic element 5 are assembled with each other at a junction 13 by gluing. The outer end 4 of the strip 2 is glued to the rigid part 18 of the flexible-strip guide of the elastic element 5 at the junction 13. The rigid part 18 includes for example a housing wherein the outer end 4 of the strip 2, which is held thanks to gluing, is inserted.

[0066] The second material, for example silicon or silicon oxide, being more fragile than the first material, the outer end 4 cannot be pressed into the housing.

[0067] In this situation, gluing is sufficient, as it is not subjected to the force or torque produced by the prestressing means 6, which is only exerted on the elastic element 5.

[0068] The elastic element 5 and the strip 2 are manufactured with different processes according to the two materials.

[0069] The elastic element 5 and/or the prestressing means 6 are produced, for example by a wire erosion process, by a laser machining process or a laser-water jet coupling, or by a LIGA type lithography process.

[0070] The strip 2 formed in the second material is for example produced by a DRIE type deep reactive-ion etching process, in particular to obtain a silicon balance-spring.

[0071] In the variant of the balance-spring made from an identical material, for example silicon, the process is preferably a DRIE type deep reactive-ion etching process.

[0072] To be able to modify the variable force or torque on the balance-spring 25, in particular on the elastic element 5, a first balance-spring stud 34 and a second balance-spring stud 35 have been represented, which are for example arranged substantially symmetrically relative to the balance shaft 24.

[0073] The first balance-spring stud 34 cooperates with the free end 15 of the lever 14, and the second balance-spring stud 35 cooperates with the second arm 47 of the fixed support 17.

[0074] The second balance-spring stud 35 includes a housing wherein the second arm 47 is inserted and force-held by friction or by pressing.

[0075] Alternatively, the second arm 47 is held in the second balance-spring stud 35 by means of a screw, not shown in the figures.

[0076] The two balance-spring studs 34, 35 are arranged on either side of the prestressing means 6 and the elastic element 5. Furthermore, the two balance-spring studs 34, 35 are rigidly connected to the lever 14 and to the fixed support 17. In other words, the first 34 and the second balance-spring stud 35 are respectively secured to the lever 14 and the fixed support 17. The assembly of the balance-spring studs and the balance-spring 25 is for example performed by gluing, brazing, soldering, by metallic glass distortion, or by a mechanical fastening.

[0077] The movement of the first balance-spring stud 34 relative to the second balance-spring stud 35 modifies the flexibility of the elastic element 5, because the movement exerts a more or less substantial force or torque on the lever 14 of the prestressing means 6, such that the flexibility of the elastic element 5 varies, and thus the flexibility of the entire balance-spring 25.

[0078] A setting device, not shown in the figures, and which is not part of the invention, makes it possible to move the first balance-spring stud 34 relative to the second balance-spring stud 35 to modify the torque or force applied to the flexible element 5.

[0079] Of course, the invention is not limited to the embodiments described with reference to the figures and variants could be considered without departing from the scope of the invention.