Hairspring mounting assembly for a watch movement, hairspring, and method for adjusting the beat and speed of a hairspring assembly

Abstract

To provide a mechanical assembly allowing secure attachment without resilient deformation of an outer last coil of a balance spring and without use of any adhesive.SOLUTION: An assembly for removable attachment of a balance spring 2 includes means 8 of retaining the balance spring 2 on one hand, and a removable locking part 10 on the other hand. A second free end 18 of an outer last coil 20 of the balance spring 2 includes attachment means in which the retaining means 8 is engaged to ensure the removable attachment of the balance spring 2 by the outer last coil 20. The attachment means is dimensioned such that, in its natural rest position, the balance spring 2 is not in contact with the retaining means 8 engaged with the attachment means. The locking part 10 for the removable attachment of the second free end 18 of the outer last coil 20 of the balance spring 2 is engaged with the retaining means 8 to lock the attachment means.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an assembly for mounting a balance spring for a timepiece movement. The present invention also relates to an adjustment method for such a mounting assembly. [Background technology]

[0002] In watchmaking, a hairspring is combined with a balance to form a regulating element commonly referred to as a hairspring balance for a mechanical watch. At first glance, the hairspring takes the form of a very thin spring that, when unstressed, is coiled around itself. When mounted, the first end of the hairspring, called the inner primary coil, is attached to a collet fitted to the balance staff, and the second end of the hairspring, called the outer final coil, is attached to a hairspring stud, a component typically attached to a balance bridge by a stud holder.

[0003] More specifically, a time base for a mechanical timepiece, also called an oscillating system, includes a hairspring balance and an escapement. The balance consists of a balance staff pivoted between a first bearing and a second bearing and connected to a balance fellow by a radial arm. The hairspring is attached to the balance staff via its inner first coil, for example by a collet, and via its outer final coil to a fixed attachment point, such as a hairspring stud carried by a stud holder.

[0004] In a very common embodiment, the escapement includes a double roller system consisting of a large roller carrying an impulse pin and a small roller with a hollow core. The escapement further includes a pallet lever, whose pallet staff is pivoted between a first bearing and a second bearing. The pallet lever is a lever connecting the forks to the entrance and exit arms. The forks, consisting of entrance and exit horns, carry the darts. The travel of the forks is limited by entrance and exit banking pins, which may be integral with the pallet bridge. The entrance and exit arms carry the entrance and exit pallets, respectively. Finally, the pallet lever cooperates with an escape wheel set, which includes an escape wheel and an escapement pinion. The assembly formed by the escape wheel and pinion is pivoted between a first bearing and a second bearing.

[0005] A balance spring is a spring that assumes a spiral shape when at rest. Wound in a plane parallel to the plane of the watch movement, the balance spring performs a single function: to make the balance oscillate around its equilibrium position (also called the rest point) at as constant a frequency as possible. When the balance is moved away from its equilibrium position by pivoting in a given direction, the balance spring contracts. This causes a restoring torque on the balance spring that tries to return the balance to its equilibrium position. During this pulsation, the balance spring relaxes. However, since the balance has gained a certain speed and therefore kinetic energy, it will move past its equilibrium position and continue in the opposite direction until the restoring torque that the balance spring exerts on the balance stops it again and causes it to rotate in the opposite direction.

[0006] The balance spring thus alternately expands and contracts, breathing, so to speak. However, during the expansion and contraction phases, many factors can prevent the balance spring from progressing isochronously. In particular, the balance spring must be resistant to oxidation and magnetism, which could cause the coils to stick together and disrupt the accuracy of the watch, or even stop it completely. On the other hand, atmospheric pressure has little effect. Over time, temperature is a major issue, as heat causes metals to expand, while cold causes them to contract. Therefore, the balance spring must be elastic enough to always return to its original shape even if it is deformed.

[0007] The material used to manufacture balance springs is usually steel. Due to its ductility, the steel used must be resistant to corrosion. Developments over the past 20 years have also suggested making balance springs from silicon. Silicon balance springs are more accurate than steel balance springs, especially since they are less susceptible to magnetic fields. However, silicon balance springs are more expensive, more fragile, and more difficult to assemble.

[0008] The balance spring must be isochronous: no matter how far the balance is rotated, the time it takes to oscillate must be the same. If the balance spring is contracted by only a few degrees, it will slowly return to its equilibrium position without storing much energy. If the balance spring is moved far from its equilibrium position, it will move very quickly in the opposite direction. The important thing is that the two journeys take the same amount of time to complete. The basic idea is that the energy available to the balance spring is not constant, and whether the watch is fully wound or at the end of its power saving period, the balance spring must still function.

[0009] The balance spring's small dimensions make it difficult to assemble. However, the way in which the ends of the balance spring are attached also has a significant impact on the accuracy of the movement's speed. In most mechanical movements, the ends of the balance spring are inserted into drilled parts and secured by pins that are manually assembled using pliers. This causes the balance spring to rotate slightly, compromising the accuracy of the movement's speed.

[0010] Another technique consists in attaching the ends of the balance spring using glue. However, this technique also has its limitations. It has been observed that the glue, due to its viscosity, exerts a tensile force on the balance spring by capillary action, which can cause the ends of the balance spring to be pressed against the walls of the balance spring stud with which they engage. The resulting deformation of the balance spring induces mechanical stresses that are detrimental to maintaining a constant speed.

[0011] To remedy this problem, the applicant has already proposed a method for attaching a hairspring, which consists in adhesively bonding the outer final coil of the hairspring in the stud using a droplet of a fluid adhesive that can be polymerized, for example, by ultraviolet radiation. That is, even if the free end of the final coil of the hairspring moves slightly under the influence of the weight of the adhesive droplet when the adhesive droplet is deposited, for example, using a syringe-type adhesive dispenser, which induces undesirable mechanical stresses in the hairspring, the adhesive is sufficiently fluid before hardening to allow the free end of the final coil of the hairspring to spontaneously return to its rest position. The mechanical stresses induced in the hairspring when the liquid adhesive droplet is deposited dissipate on their own, and the consistency of the hairspring's speed is not affected by the adhesive bonding effected thereon.

[0012] The above solution thus allows the balance spring to be mounted in the stud by the free end of its outer final coil, while eliminating all or at least most of the mechanical stresses normally induced in the balance spring during assembly. This significantly improves the consistency of the balance spring's speed. However, in use, the applicant has nevertheless noticed that the hardened adhesive pad, which forms when droplets of liquid adhesive used to attach the free end of the balance spring's outer final coil polymerize, sometimes tends to peel off from the stud. This, of course, immediately causes the failure of the watch movement in which the balance spring is installed. Such a situation is due in particular to problems with the surface condition of the stud, which prevents the adhesive pad from fully adhering to the stud, but also to creep and aging of the adhesive pad over time. Furthermore, as the ambient temperature increases, most adhesives soften, resulting in a change in the effective length and therefore the stiffness of the balance spring, which negatively affects the speed of the watch movement.

[0013] Finally, it should be noted that, particularly in the case of high-end watch movements, the use of adhesives or synthetic products that are not compatible with the high level of finish and expertise required for such movements is avoided as far as possible.

[0014] Patent Document 1 discloses a hairspring for a balance assembly of a mechanical timepiece movement, in which the free end of the outer end coil of the hairspring includes an elastically deformable opening for receiving and clamping a hairspring stud-type mounting element. Preferably, the mounting element has a cylindrical shape with a circular cross-section, which includes a flat area against which the free end of the outer end coil of the hairspring contacts to prevent the free end from rotating around the mounting element during operation of the movement. The mounting element allows the free end of the outer end coil of the hairspring to be mounted without the need for additional mounting means such as pins or adhesive. Furthermore, by adjusting the position of the free end of the outer end coil of the hairspring relative to the mounting element, it is possible to adjust the height of the free end on the mounting element. This is made possible by the fact that the free end of the outer end coil of the hairspring frictionally engages with the mounting element. However, this has problems. For example, in the event of a shock, there is a risk that the free end of the outer final coil will shift position relative to its mounting element or even become dislodged from this mounting element. This would, at best, alter the speed accuracy of the balance spring balance assembly and, at worst, cause the watch to malfunction. It should also be noted that if the mounting of the outer final coil of the balance spring is secured by frictional forces resulting from the elastic contact between the mounting element and an opening in the free end of the outer final coil of the balance spring, this does not guarantee the true durability of the balance spring, inasmuch as these frictional forces tend to be relaxed over time and with wear. The frictional force between the edge of the opening in the free end of the outer final coil of the balance spring and the mounting element quickly becomes insufficient to securely fasten the balance spring to this mounting element. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] European Patent Application Publication No. 1515200 Summary of the Invention

[0016] The object of the present invention is to alleviate the above and other problems by providing a mechanical assembly which allows a hairspring for a timepiece movement to be securely mounted without elastic deformation of the outer end coil and without the use of adhesives, so that, if necessary, the hairspring can be disassembled and reassembled without risk of damage.

[0017] To this end, the present invention relates to an assembly including a balance bridge for the removable mounting of a hairspring of a timepiece movement, the assembly comprising, on the one hand, a hairspring and, on the other hand, means for holding the hairspring and a removable locking element, the hairspring including a coil winding extending between a first free end of an inner first coil and a second free end of an outer final coil, the second free end of the hairspring's outer final coil having mounting means engaged with a retaining means for releasably mounting the hairspring by the outer final coil, the mounting means being dimensioned such that, in its natural reset position, the hairspring does not come into contact with the retaining means engaged with the mounting means, and a locking element ensuring the removable mounting of the second free end of the hairspring's outer final coil is mounted on the retaining means to lock the mounting means.

[0018] In a particular embodiment of the invention, the attachment means is an opening formed in the second free end of the outer final coil of the balance spring.

[0019] In a particular embodiment of the invention, the second free end of the outer final coil of the balance spring is formed with an opening and is made integral with the balance spring assembly.

[0020] In another particular embodiment of the invention, the opening is formed by a curved portion of the second free end of the outer final coil of the balance spring.

[0021] In yet another particular embodiment of the invention, the second free end of the outer final coil of the balance spring is provided with a plate formed with an opening.

[0022] In yet another particular embodiment of the present invention, the plate is fixed to the second free end of the outer final coil of the balance spring.

[0023] In yet another particular embodiment of the present invention, the plate is welded to the second free end of the outer final coil of the balance spring.

[0024] In yet another embodiment of the present invention, the openings are oval in shape.

[0025] In yet another embodiment of the present invention, the oblong opening has a major axis that is continuous with the outer final coil.

[0026] In yet another particular embodiment of the present invention, the retaining means includes a post arranged in an opening formed in the second free end of the outer final coil of the balance spring.

[0027] In yet another particular embodiment of the invention, the post is made integral with the balance bridge of the timepiece movement.

[0028] In yet another particular embodiment of the present invention, the retaining means includes a support member formed by a stud on which a post is mounted.

[0029] In yet another particular embodiment of the present invention, the support component is arranged in a recess formed in the balance bridge.

[0030] In yet another particular embodiment of the present invention, the support piece is arranged in the recess by a friction fit.

[0031] In yet another particular embodiment of the present invention, the support piece is threaded into the recess.

[0032] In yet another particular embodiment of the invention, a retaining piece is arranged between the balance bridge and the support piece to prevent accidental unscrewing of the support piece.

[0033] In yet another particular embodiment of the present invention, the retaining piece is a spring washer.

[0034] In yet another embodiment of the present invention, the locking component is a washer removably attached to the post.

[0035] In yet another embodiment of the present invention, the washer is pressed onto the post.

[0036] In yet another particular embodiment of the invention, a flexible element intended to modify the stiffness of the balance spring is arranged between the second free end of the outer final coil of the balance spring and a lever surrounding the coil winding and terminating in a plate formed with an opening.

[0037] The invention further relates to a method for adjusting the speed of a balance spring mounted by means of a mounting assembly according to the invention, wherein mounting means included in a second free end of the outer final coil of the balance spring are engaged with a post of a support part, the support part is pivoted in one direction or the other, as required, until the post is no longer in contact with the mounting means of the balance spring, the beat of the balance spring balance assembly is adjusted by pivoting this balance spring balance assembly around the balance staff until the impulse pin of the balance roller is aligned with the escapement line passing through the balance staff and the pallet staff, thereafter, once the adjustment of the beat of the balance spring balance assembly is completed, it is again ensured that the post of the support part does not come into contact with the mounting means of the balance spring and, if applicable, the support part is again rotated to move the post away from the mounting means of the balance spring, and then a removable locking part is attached to the post to lock the second free end of the outer final coil of the balance spring.

[0038] The present invention further relates to a method for adjusting the speed of a balance spring assembly having a balance spring mounted by a mounting assembly according to the present invention, wherein a removable locking part is attached to a post to lock the second free end of the outer final coil of the balance spring, and the support part is then pivoted clockwise or counterclockwise to drive the second free end of the outer final coil of the balance spring.

[0039] Thanks to these characteristics, the invention provides an assembly that allows the hairspring of a timepiece movement to be mounted in a removable and repositionable manner without the aid of adhesives, and that ensures the immobilization of the free end of the outer final coil of the hairspring without inducing mechanical stresses on said hairspring and, in particular in the plane in which the windings of the coils of said hairspring extend, so as not to affect the regularity of the speed of the timepiece movement. [Brief explanation of the drawings]

[0040] Other features and advantages of the present invention will become apparent from the following detailed description of one embodiment, which is given by way of non-limiting example only and with reference to the accompanying drawings, in which:

[0041] [Figure 1] 1 is a general perspective view of an assembly for removably mounting a balance spring of a timepiece movement, in its simplified embodiment. FIG. [Figure 2] 1 is a general perspective view of an assembly for removably mounting a balance spring of a timepiece movement, in an improved embodiment thereof; FIG. [Figure 3] FIG. 3 is a top view of a silicon balance spring including a first flexible arm and a second flexible arm used in the mounting assembly of FIG. 2. [Figure 4] A perspective view of a balance spring, with a plate integral with the outer final coil and an opening formed in the plate to receive the post. [Figure 5]1 is a perspective view of a balance spring with a plate attached to the free end of the outer final coil of the balance spring, the plate having an opening for receiving a post. [Figure 6] 1 is a perspective view of a balance spring, the outer final coil of which is curved to form an opening that receives the post. [Figure 7] Schematic diagram showing when the post is made integral with the balance bridge of the watch movement. [Figure 8] FIG. 10 is a schematic diagram showing the case where the holding means includes a support part formed by a stud with a post mounted thereon, the stud being aligned by a friction fit in a recess formed in the balance bridge. [Figure 9] This shows the case where the holding means includes a support member formed by a stud with a post mounted thereon, arranged in a recess formed in the balance bridge by screwing with a washer interposed between the balance bridge and the support member to prevent accidental unscrewing. [Figure 10] A perspective view of a balance spring, the outer final coil of which is curved to form a hook that receives a post. [Figure 11] Figures 11 and 12 show, respectively, assembled and disassembled cases in which the retaining means are arranged in the form of a support piece placed in a recess formed in the balance bridge, the outer final coil of the balance spring being capped by a locking piece provided with a post which is received in an opening formed in the support piece. [Figure 12] Figures 11 and 12 show, respectively, assembled and disassembled cases in which the retaining means are arranged in the form of a support piece placed in a recess formed in the balance bridge, the outer final coil of the balance spring being capped by a locking piece provided with a post which is received in an opening formed in the support piece. DETAILED DESCRIPTION OF THE INVENTION

[0042] The present invention is derived from the general inventive idea of ​​providing a mechanical assembly that allows the second free end of the outer final coil of a balance spring for a timepiece movement balance assembly to be attached without the use of adhesive. By making it possible to dispense with the use of adhesives, the present invention avoids the problems associated with such materials, particularly in terms of aging and creep, as well as image. It is clearly understood that, particularly in the field of high-end watches, it is desirable to avoid, as much as possible, the need to use adhesives to assemble mechanical components. According to another of its advantages, the mechanical assembly of the present invention allows the second free end of the outer final coil of a balance spring to be attached in a removable manner, so that the position of the balance spring can be readjusted as needed, even when the watch is returned to the workshop. Another advantage of the mechanical assembly of the present invention is that it allows the second free end of the outer final coil of a balance spring for a timepiece movement to be attached without mechanical stresses being induced at this second end, particularly in the plane in which the coil windings forming the balance spring extend. This is highly favorable in terms of the speed accuracy of the balance spring balance assembly.

[0043] The mounting assembly according to the present invention, generally referred to by the general reference number 1, is intended for the removable mounting of a hairspring 2 of a timepiece movement including a balance bridge 4.

[0044] In particular, as shown in FIG. 1, the mounting assembly 1 includes a balance spring 2 as well as a retaining means 8 and a removable locking element 10 .

[0045] As can be seen from FIG. 1 , the hairspring 2 comprises a coil winding 12 extending between a first free end 14 of the inner first coil 16 and a second free end 18 of the outer final coil 20. According to the invention, the second free end 18 of the outer final coil 20 of the hairspring 2 comprises an attachment means in the form of an opening 22, in a preferred but non-limiting embodiment of the invention, in which a retaining means 8 is engaged to ensure the removable attachment of the hairspring 2 by its outer final coil 20. The opening 22 is dimensioned such that, in the natural rest position of the hairspring 2, an edge 24 of this opening 22 does not come into contact with the mechanical attachment means 8 engaged therein. In other words, the attachment of the hairspring 2 by the attachment assembly 1 according to the invention does not induce any stresses in the hairspring 2 in the XY plane in which it extends, i.e., without affecting the accuracy of the rate. A removable locking element 10 is intended to ensure the removable attachment of the second free end 18 of the outer final coil 20 of the balance spring 2 and is engaged, preferably by pushing, with the means 8 that follow and hold the balance spring 2.

[0046] According to a particular embodiment of the invention, the opening 22 provided in the second free end 18 of the outer final coil 20 of the balance spring 2 is preferably, but not limited to, oval in shape, and the main axis 26 extends continuously through the outer final coil 20 (see FIG. 3).

[0047] In the embodiment shown in FIGS. 4 to 6, the opening 22 is oval in shape with a radius of curvature R centered on the center 27 of the coil winding 12 .

[0048] The opening 22 can be embodied in a variety of ways.

[0049] In one embodiment of the present invention, the second free end 18 of the outer final coil 20 of the hairspring 2 is formed with an opening 22 and is made integral with the hairspring 2 assembly. That is, the outer final coil 20 of the hairspring 2 can be provided with an integrally made plate 28 with the opening 22 formed therein (FIG. 4). Conversely, the plate 28 can be attached to the second free end 18 of the outer final coil 20 of the hairspring 2 by a joining process, for example welding (FIG. 5). It is also possible for the opening 22 to be formed by a curved portion 30 of the second free end 18 of the outer final coil 20 of the hairspring 2 (FIG. 6).

[0050] The retaining means 8 includes a post 32 arranged to engage an opening 22 formed in the second free end 18 of the outer final coil 20 of the balance spring 2 .

[0051] In a first embodiment, the post 32 is made integral with the balance bridge 4 of the watch movement (FIG. 7).

[0052] According to another embodiment of the invention, the retaining means 8 comprises a support part 34 formed by a stud 36 on which the post 32 is mounted. This support part 34 is arranged in a recess 38 formed in the balance bridge 4. The support part 34 is positioned in the recess 38 either by a friction fit (FIG. 8) or by screwing (FIG. 9). When the support part 34 is screwed into the recess 38, the support part 34 is externally threaded and the recess 38 has a complementary thread on its inner wall 40. To prevent accidental unscrewing of the support part 34, a retaining part 42 such as a spring washer may be arranged between the balance bridge 4 and the support part 34 (FIG. 9).

[0053] The removable locking component 10 is a washer that is removably attached to the post 32, typically by a push fit.

[0054] In its simplified embodiment, the mounting assembly 1 according to the present invention allows for adjusting the beat of the balance spring assembly 44. Furthermore, in its preferred embodiment, the mounting assembly 1 according to the present invention not only allows for adjusting the beat of the balance spring assembly 44, but also for adjusting the speed of such balance spring assembly 44.

[0055] As already mentioned above, the mounting assembly 1 according to the invention is first mounted by engaging the opening 22 provided in the second free end 18 of the outer final coil 20 of the balance spring 2 with the post 32 of the support part 34. Normally, the entire mechanical assembly formed by the balance spring 2, the balance spring assembly 44 comprising said balance spring 2, and the holding means 8 is dimensioned such that, when the post 32 of the support part 34 is engaged in the opening 22 of the balance spring 2, the edge 24 of the opening 22 of the balance spring 2 does not come into contact with the post 32 engaged in this opening 22. However, in the rare event that this is not the case, the invention advantageously allows the support part 34 to be pivoted slightly in one direction or the other until the post 32 is no longer in contact with the edge 24 of the opening 22 of the balance spring 2. The beat of the balance spring balance assembly 44 is then adjusted by rotating the balance spring balance assembly 44 around the balance staff 46 until the impulse pin 48 of the balance roller 50 is aligned with the escapement line that passes through the balance staff 46 and the pallet staff (not shown in the drawings). Once the adjustment of the beat of the balance spring balance assembly 44 is complete, it is again ensured that the post 32 of the support piece 34 does not contact the edge 24 of the opening 22 of the balance spring 2. As mentioned above, in the extremely unlikely event that this is not the case, the present invention can again rotate the support piece 34 to move the post 32 away from the edge 24 of the opening 22 of the balance spring 2, and then drive the washer onto the post 32 to lock the second free end 18 of the outer final coil 20 of the balance spring 2. In the opposite case, i.e. when no contact is found between the edge 24 of the opening 22 of the balance spring 2 and the post 32 of the support part 34, the balance spring 2 can be locked directly by attaching a washer to the post 32.

[0056] It is of course understood that if the support part 34 is made integral with the balance bridge 4, the support part 34 cannot be pivoted.

[0057] 2, it is possible to adjust not only the beat of the balance spring assembly 44, but also the speed of the balance spring assembly 44. The operation of adjusting the speed of the balance spring assembly 44 is performed after the second free end 18 of the outer final coil 20 of the balance spring 2 has been locked by attaching a washer to the post 32. At this point, the support part 34 is pivoted clockwise or counterclockwise, thereby driving the second free end 18 of the outer final coil 20 of the balance spring 2.

[0058] 3 shows that the hairspring 2 comprises a flexible element 52 consisting of a pivot 54 including a first non-intersecting flexible blade 56 and a second non-intersecting flexible blade 58, and a rigid part 60. The first flexible blade 56 and the second flexible blade 58 are laterally joined to an elongated fixed support part 62 on the one hand, and are joined to the pivot 54 by moving towards each other on the other hand. That is, the flexible blades 56, 58 move towards each other from the fixed support part 62 to the pivot 54. The fixed support part 62 is attached to a mounting part 62a that is integral with the bridge 4. The second free end 18 of the outer final coil 20 of the hairspring 2 is joined to the pivot 54. In the drawing, a variable torque is exerted on an additional blade 63 connecting the outer final coil 20 to the rigid part 60, thereby modifying the stiffness of this additional blade and, consequently, the stiffness of the balance spring 2 and, therefore, the speed of the balance spring balance assembly 44. To this end, the balance spring 2 is stretched beyond its flexible element 52 by a lever 64 that bypasses the coil winding 12. The lever 64 terminates in a plate 28 provided with an opening 22 according to the invention. Torque is transmitted to the balance spring 2 via the lever 64 and the flexible element 52. For a complete description of the balance spring 2 used in this modified embodiment of the invention, reference is made to European Patent Application No. 21202213.1 filed by the applicant.

[0059] It goes without saying that the present invention is not limited to the embodiments just described, and various simple modifications and alternative embodiments can be envisaged by those skilled in the art without departing from the scope of the present invention as defined by the appended claims.

[0060] The post 32 can be made integral with the balance bridge 4. If the support part 34 is a separate part that is attached by a press fit into a recess 38 machined in the balance bridge 4, the support part 34 can be pivoted both clockwise and counterclockwise. When the support part 34 is pivoted, the post 32 is also pivoted, so that the post 32 does not come into contact with the edge 24 of the profile of the opening 22 made in the free end 18 of the outer final coil 20 of the balance spring 2. This means that the balance spring 2 can be spontaneously placed in its natural rest position free from mechanical stress. This is the most favorable solution for the speed accuracy of the balance spring balance assembly 44.

[0061] Typically, the balance spring 2, especially if made of silicon, is manufactured to very tight tolerances, so that the position of the geometric centre of the opening 22 made in the free end 18 of the outer final coil 20 of the balance spring 2 is known very accurately in advance. This makes it possible to accurately position the post 32 on the balance bridge 4, or alternatively to position the support piece 34 corresponding to the assembly formed by the stud 36 and the post 32, in a recess 38 provided in the balance bridge 4 for this purpose.

[0062] If the balance spring 2 is made of silicon, the free end 18 of the outer final coil 20 of the balance spring 2, in which the opening 22 is formed, is made integral with the balance spring 2 assembly. If the balance spring 2 is made of a metal alloy, the opening 22 for receiving the post 32 of the support part 34 can be formed by simply bending the free end 18 of the outer final coil 20 of the balance spring 2. It is also possible to attach, typically by welding, to the free end 18 of the outer final coil 20 of the balance spring 2, a plate 28 in which the opening 22 for receiving the post 32 of the support part 34 is formed.

[0063] In the extremely unlikely event that, after installation of the balance spring 2 and engagement of the post 32 in the opening 22 provided in the free end 18 of the outer final coil 20 of the balance spring 2, the edge 24 of this opening 22 is observed to come into mechanical contact with the post 32 at any point, the invention advantageously allows the support part 34 to be pivoted until mechanical contact is no longer observed. That is to say, whatever the circumstances, the invention makes it possible to guarantee immobilization of the free end 18 of the outer final coil 20 of the balance spring 2 without inducing stresses in the XY plane in which the balance spring 2 extends. This is highly advantageous for the speed accuracy of the balance spring assembly 44.

[0064] In a simplified alternative embodiment of the invention, there is a single attachment point for the free end 18 of the outer final coil 20 of the balance spring 2. That is, the post 32 of the support piece 34 engaged in the opening 22 formed in the free end 18 of the outer final coil 20 of the balance spring 2 acts as a balance spring stud, and thus only the beat of the balance spring assembly 44 can be adjusted.

[0065] In an improved alternative embodiment of the present invention, two attachment points are present and the balance spring 2 is preferably made of silicon. In this case, two attachment points are present and both the beat and speed of the balance spring balance assembly 44 can be adjusted. It is further understood that, thanks to the present invention, the speed of the balance spring balance assembly 44 can be fine-tuned in different ways, for example, by modifying the inertia of the balance, by adding or removing material, or by screwing in or unscrewing weights. It is also possible to adjust the speed of the balance spring balance assembly 44 by modifying the stiffness of the balance spring 2 according to the present invention. Some balance spring balance assemblies can also be adjusted in both ways simultaneously.

[0066] The stud 36 of the support part 34 may be threaded to allow fine adjustment of its height along an axis Z perpendicular to the support surface provided by the support part 34. To prevent the threaded support part 34 from accidentally coming loose, a retaining part 42, for example of the spring washer type, may be arranged between the threaded support part 34 and the surface of the balance bridge 4 to lock the threaded stud 36. Thanks to the invention, it is possible to adjust the speed rate of the balance spring balance assembly 44 by changing the stiffness of the balance spring 2, which is attached to the balance staff 46 by means of a collet 66. This is much easier than adjusting the speed of a balance spring balance assembly by modifying the inertia of the balance, for example by adding or removing material or by moving weights, screws, etc.

[0067] According to a particular embodiment of the invention shown in FIG. 10 , the attachment means may have an open geometry, for example in the form of a hook 68, into which a retaining means 8 engages, ensuring a removable attachment of the hairspring 2 by its outer final coil 20. This retaining means 8 is of the type of post 32, arranged in the interior space bounded by the hook 68 and held in place by a retaining piece 42. Normally, when the hairspring 2 is fitted, there should be no mechanical contact between the hook 68 and the post 32. However, if this is not the case, the support piece 34 may be rotated until no mechanical contact is observed.

[0068] According to a particular embodiment of the invention, the retaining means 8 comprises a support piece 70 arranged in a recess 72 formed in the balance bridge 4. The support piece 70 is arranged in the recess 72 either by friction fit or by screwing. The free end 18 of the outer final coil 20 of the balance spring 2 rests on this support piece 70 and is capped by a locking piece 74 provided on its underside with a post 76 received in an opening 78 made in the support piece 70. [Explanation of symbols]

[0069] 1 Mounting Assembly 2. Hairspring 4 Balance cock 8. Means of retention 10 Removable locking parts 12 Coil Winding 14 1st free end 16 Inner first coil 18 Second free end 20 outer final coil 22 Aperture 24 Edge 26 Spindle 27 center 28 Plates 30 curved part 32 posts 34 Support parts 36 studs 38 Recess 40 Inner wall 42 Retaining parts 44 Hairspring balance assembly 46 Balance Staff 48 Impulse Pin 50 Balance Roller 52 Flexible elements 54 Axis 56 First flexible blade 58 Second flexible blade 60 Rigid parts 62 Fixed support 62a Mounting parts 63 Additional Blade 64 Lever 66 Colette 68 Hook 70 Support parts 72 recess 74 Lock parts 76 posts 78 Aperture

Claims

1. Assembly (1) for the removable mounting of a hairspring (2) of a timepiece movement including a balance bridge (4), comprising: said assembly comprising, on the one hand, a retaining means (8) for said balance spring (2) and, on the other hand, a removable locking element (10); The balance spring (2) includes a coil winding (12) extending between a first free end (14) of an inner first coil (16) and a second free end (18) of an outer final coil (20); a second free end (18) of the outer final coil (20) of the balance spring (2) comprising attachment means with which the retaining means (8) are engaged to ensure a removable attachment of the balance spring (2) with its outer final coil (20); said attachment means being dimensioned such that in its natural rest position it does not come into contact with said holding means (8) engaged therewith; Assembly (1), wherein the removable locking element (10) for removably attaching the second free end (18) of the outer final coil (20) of the balance spring (2) is mounted on the holding means (8) for locking the attachment means.

2. Assembly (1) according to claim 1, wherein said attachment means is an opening (22) provided in the second free end (18) of the outer final coil (20) of the balance spring (2).

3. 3. The assembly (1) of claim 2, wherein the opening (22) is oval in shape and has a major axis (26) that is continuous with the outer final coil (20).

4. 3. The assembly (1) according to claim 2, wherein the second free end (18) of the outer final coil (20) of the hairspring (2), in which the opening (22) is formed, is made integral with the hairspring (2) assembly.

5. 3. An assembly (1) according to claim 2, wherein the opening (22) is formed in a curved portion (30) of the second free end (18) of the outer final coil (20) of the balance spring (2).

6. 3. An assembly (1) according to claim 2, wherein the second free end (18) of the outer final coil (20) of the balance spring (2) is provided with a plate (28) in which the opening (22) is formed.

7. 7. An assembly (1) according to claim 6, wherein said plate (28) is fixed to the second free end (18) of the outer final coil (20) of said balance spring (2).

8. 8. An assembly (1) according to claim 7, wherein the plate (28) is welded to the second free end (18) of the outer final coil (20) of the balance spring (2).

9. 2. An assembly (1) according to claim 1, wherein the retaining means (8) comprises a post (32; 76) arranged to engage in an opening (22) provided in the second free end (18) of the outer final coil (20) of the balance spring (2).

10. 10. An assembly (1) according to claim 9, wherein said post (32) is made integral with the balance bridge (4) of said timepiece movement.

11. An assembly (1) as described in claim 9, wherein the post (32) is mounted on a support part (34) formed by a stud (36).

12. Assembly (1) according to claim 11, wherein the support part (34) is placed in a recess (38) formed in the balance bridge (4).

13. Assembly (1) according to claim 12, wherein the support part (34) is arranged in the recess (38) by means of a friction fit.

14. Assembly (1) according to claim 12, wherein the support part (34) is screwed into the recess (38).

15. 15. An assembly (1) according to claim 14, wherein a retaining part (42) is arranged between the balance bridge (4) and the support part (34) to prevent accidental unscrewing of the support part (34).

16. Assembly (1) according to claim 15, wherein the retaining part (42) is a spring washer.

17. 10. The assembly (1) according to claim 9, wherein the removable locking element (10) is a washer removably attached to the post (32).

18. 18. The assembly (1) of claim 17, wherein the washer is pressed onto the post (32).

19. 10. The assembly (1) according to claim 9, wherein the post (76) is received in an opening (78) formed in a support part (70) disposed in a recess (72) formed in the balance bridge (4), and the second free end (18) is capped by a locking part (74) provided with the post (76).

20. 3. An assembly (1) according to claim 2, wherein a flexible element (52) arranged to modify the stiffness of the balance spring (2) is arranged between the second free end of the outer final coil of the balance spring and a lever (64) surrounding the coil winding (12), the opening (22) being provided in the free end of the lever (64).

21. A method for adjusting the beat of a balance spring assembly including a balance spring (2) mounted by an assembly (1) according to claim 11, comprising the steps of: the attachment means included in the second free end (18) of the outer final coil (20) of the balance spring (2) is engaged with a post (32) of the support part (34); The support part (34) is pivoted in one direction or the other, as required, until the post (32) is no longer in contact with the attachment means of the balance spring (2); the beat of the balance spring balance assembly (44) is adjusted by pivoting the balance spring balance assembly (44) about the balance staff (46) until the impulse pin (48) of the balance roller (50) is aligned with an escapement line passing through the balance staff (46) and the pallet staff, then once the adjustment of the beat of the balance spring balance assembly (44) is completed, it is ensured that the post (32) of the support part (34) does not again come into contact with the attachment means of the balance spring (2), and if applicable, the support part (34) is again rotated to move the post (32) away from the attachment means of the balance spring (2), after which the removable locking part (10) is pressed onto the post (32) to lock the second free end (18) of the outer final coil (20) of the balance spring (2).

22. A method for adjusting the speed of a hairspring balance assembly (44), comprising the steps of:

12. The method according to claim 11, wherein the hairspring of the hairspring balance assembly is mounted by the assembly according to claim 11, and the removable locking part is pressed onto the post to lock the second free end of the outer final coil of the hairspring, and then the support part is pivoted clockwise or counterclockwise to drive the second free end of the outer final coil of the hairspring.

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