Clock assembly with balance spring and studs

Abstract

To provide a horological assembly comprising a balance spring and a stud.SOLUTION: The invention relates to an assembly (1) for attaching a free end (8) of an outer last coil (10) of a balance spring (12) for a horological movement. The attachment assembly (1) includes a stud (2) and a blocking element (14). The stud (2) comprises a groove (6) with which the free end (8) of the outer last coil (10) of the balance spring (12) is engaged. The blocking element (14) is also engaged with the groove (6) so as to contact the outer last coil (10) of the balance spring (12). The attachment assembly (1) further includes a clamping member (16) which presses the blocking element (14) against the free end (8) of the outer last coil (10) of the balance spring (12) so that the free end (8) of the outer last coil (10) of the balance spring (12) is immobilized in the groove (6) of the stud (2).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a hairspring for a balance of a watch movement. The present invention further relates to a stud for mounting the outer end coil of such a hairspring. The present invention further relates to a method for manufacturing such a hairspring. [Background technology]

[0002] In the field of horology, the hairspring associated with the balance generally forms a regulating member, called the sprung balance, for mechanical timepieces. The hairspring is initially seen as a very thin spring wound concentrically when unstressed. In the installed state, the first end of the hairspring, called the inner first coil, is attached to a collet fitted to the balance staff, and the second end of the hairspring, called the outer final coil, is usually attached to a stud, also called the balance cock, a part attached by a stud holder on the bridge for the balance.

[0003] More specifically, the time base for a mechanical timepiece, also called an oscillating system, comprises a sprung balance pair and an escapement. The balance consists of a balance staff pivoted between a first and a second bearing and connected to the balance rim by a radial arm. The balance spring is attached by its inner first coil to the balance staff, for example by a collet, and by its outer final coil to a fixed mounting point, such as a stud supported by a stud holder.

[0004] In its very widespread embodiment, the escapement comprises a double roller system consisting of a table roller supporting the impulse pin and a safety roller formed with a notch. The escapement further comprises an anchor lever with an anchor staff pivoted between a first bearing and a second bearing. The anchor lever is composed of a lever connecting a fork to an entry arm and an exit arm. The fork is composed of an entry horn and an exit horn and supports the dart. The movement of the fork is limited by an entry bank pin and an exit bank pin, which can be made integral with the anchor bridge. The entry arm and the exit arm support respectively an entry pallet and an exit pallet. Finally, the anchor lever cooperates with an escape wheel set comprising an escape wheel and an escape pinion, this assembly formed by the escape wheel and the escape pinion being pivoted between a first bearing and a second bearing.

[0005] A balance spring is a spring that, at rest, assumes a spiral shape. Wound in a horizontal plane parallel to the plane of the clock movement, it serves the sole purpose of making the balance oscillate with as constant a frequency as possible around its equilibrium position, also called the dead center. When the balance leaves its equilibrium position by pivoting in a given direction, the balance spring contracts. This creates a restoring torque on the balance spring, which returns it to its equilibrium position. During this pulsation, the balance spring stretches. However, once the balance has acquired a certain speed, i.e. kinetic energy, it will exceed its equilibrium position in the opposite direction to the previous one, until the restoring torque exerted on it by the balance spring stops it again and forces it to rotate in the other direction.

[0006] The hairspring therefore expands and contracts alternately, and is said to breathe. However, many factors come into play in preventing the hairspring from unfolding isochronously during the expansion and contraction phases. In particular, the hairspring must be resistant to oxidation and magnetism, which can cause the coils to stick together and impair the accuracy of the watch, or even stop it completely. On the other hand, atmospheric pressure has a smaller effect. For a long time, temperature was the main problem, since metals expand when hot and contract when cold. The hairspring must therefore be elastic so that it can always return to its original shape if it is deformed.

[0007] The material used to manufacture the hairspring is usually steel. The steel used must be ductile and therefore resistant to corrosion. Developments over the last 20 years have also proposed to manufacture hairsprings from silicon. Silicon hairsprings offer a higher rate of accuracy than traditional steel hairsprings, especially since they are less susceptible to magnetic fields. However, they are more difficult to assemble, more expensive and more prone to breaking.

[0008] The hairspring must be isochronous: no matter how many times the balance turns, the time it takes to oscillate must always be the same. If the hairspring contracts only a few degrees, it stores very little energy and slowly returns to its equilibrium position. If it moves too far away from its equilibrium position, it moves in the opposite direction very quickly. The important thing is that the time it takes to complete these two movements is the same. The underlying idea is that the energy available to the hairspring is not constant, and the hairspring must keep working whether the watch is fully wound or at the end of its power reserve.

[0009] The balance spring is difficult to assemble due to its small dimensions. However, the way in which the ends of the balance spring are attached also has a significant impact on the accuracy of the speed of the watch movement. In most mechanical watch movements, both ends of the balance spring are fixed by pins that are inserted into drilled parts and then forcibly assembled by hand using pliers. This can cause the balance spring to rotate slightly, which negatively affects the accuracy of the speed of the movement.

[0010] Another technique consists in attaching the ends of the hairspring using an adhesive. However, this technique also has limitations: it has been observed that the adhesive, due to its viscosity, exerts a pulling force on the hairspring by capillary action, forcing the ends of the hairspring against the walls of the studs with which they mesh. The resulting deformation of the hairspring induces mechanical stresses in it that are detrimental to maintaining a consistent speed.

[0011] To overcome these problems, the applicant has already proposed a method for mounting the hairspring, which consists in adhesively bonding the outer final coil of the hairspring into the stud, for example by means of a drop of a polymerizable fluid adhesive, for example by means of ultraviolet light. Thus, even if the drop of adhesive is applied, for example by means of a syringe-type adhesive dispenser, the free end of the final coil of the hairspring will move slightly under the effect of the weight of the drop of adhesive, thereby inducing undesirable mechanical stresses in the hairspring, but the adhesive has sufficient fluidity before hardening, so that the free end of the final coil of the hairspring can return spontaneously to its rest position. Thus, the mechanical stresses induced in the hairspring when dropping the liquid adhesive will naturally disappear and the consistency of the speed of the hairspring will not be affected by the adhesive bonding operation carried out on the hairspring.

[0012] The above solution therefore allows the hairspring to be mounted in a stud by the free end of its outer final coil, while eliminating all, or at least most, of the mechanical stresses that are usually induced in such a hairspring during its assembly. This significantly improves the consistency of the hairspring's speed. However, the applicant has noticed that during use, the hardened adhesive pad, which is formed when a drop of liquid adhesive used to attach the free end of the outer final coil of the hairspring polymerizes, tends to peel off from the stud from time to time. This, of course, immediately leads to the failure of the watch movement in which this hairspring is installed. Such a situation is caused, among other things, by problems with the surface condition of the stud, which prevents the adhesive pad from completely adhering to the stud, and by the deterioration of the adhesive pad over time. Moreover, an increase in the ambient temperature causes most of the adhesive to soften, which results in a change in the effective length and therefore in the stiffness of the hairspring, thus negatively affecting the speed of the watch movement.

[0013] Finally, it should be noted that, especially in the case of top-end watch movements, the use of glues and synthetic products is avoided as much as possible. Summary of the Invention [Problem to be solved by the invention]

[0014] It is an object of the present invention to overcome the aforementioned problems and others by providing an assembly for mounting a hairspring, the outer final coil of which can be securely fixed without the use of glues, pins or even manual procedures such as clamping or crimping, the success of which often depends on the dexterity of the operator. [Means for solving the problem]

[0015] To this end, the invention relates to an assembly for mounting a free end of an outer final coil of a hairspring for a timepiece movement, the mounting assembly comprising a stud and a blocking element, the stud being provided with a groove into which the hairspring engages at a point along its length, the blocking element also engaging in the groove and in contact with the hairspring, the mounting assembly further comprising a clamping member pressing the blocking element against the free end of the outer final coil of the hairspring, the free end of the outer final coil of the hairspring being fixed in the groove of the stud.

[0016] According to one particular embodiment of the invention, the balance spring meshes, via the free end of its outer final coil, in the groove of the stud.

[0017] According to another particular embodiment of the invention, the free end of the outer final coil of the balance spring is fixed by mechanical clamping and blocking in a direction perpendicular to the plane in which this free end of the balance spring extends.

[0018] According to yet another particular embodiment of the invention, the groove extends from the outer wall of the stud towards its interior.

[0019] According to yet another particular embodiment of the invention, the groove has a height and the blocking element has a thickness such that, when the blocking element engages in this groove, sufficient space remains to be left to be able to engage with the free end of the outer final coil of the hairspring within the groove.

[0020] According to yet another particular embodiment of the invention, the space in which the free end of the outer final coil of the balance spring meshes extends between the blocking element and the back side of the groove.

[0021] According to yet another particular embodiment of the invention, the free end of the outer final coil of the balance spring terminates in a plate that is attached to or made integral with said free end.

[0022] According to yet another particular embodiment of the invention, the stud is formed with a hole into which the fastening member engages, the fastening member extending into the groove and pressing against the blocking element, which in turn presses against the free end of the outer final coil of the hairspring.

[0023] According to yet another particular embodiment of the present invention, the fastening member is a threaded rod and the hole is threaded.

[0024] According to yet another particular embodiment of the invention, the blocking element is a clamp provided with two jaws connected to each other at their distal ends, the two jaws defining an open space between them on the proximal side.

[0025] According to yet another particular embodiment of the invention, the stud comprises a wall that bounds the groove.

[0026] According to yet another particular embodiment of the invention, an inner surface of one of the jaws of the clamp has a surface that extends away from the wall of the stud, in the direction of engagement of the clamp with the stud.

[0027] According to yet another particular embodiment of the invention, the inner surface of the jaws of the clamp is provided with a recess, the shape of which is complementary and matches the shape of the wall so that the clamp grips the wall with sufficient holding force while the operator engages the outer final coil of the balance spring in the groove made in the stud.

[0028] According to yet another particular embodiment of the invention, the balance spring mounting assembly can be disassembled.

[0029] Thanks to these characteristics, the invention provides an assembly for mounting the free end of the outer curve of a hairspring for a watch movement, with many advantages, including in particular the fact that the hairspring can be mounted without adhesive, regardless of the type of material used to manufacture such a hairspring. The watchmaker is therefore completely free to choose the material from which the hairspring is made, and, moreover, the mounting assembly according to the invention is dismantlable, since the free end of the hairspring is not bonded. Moreover, since the free end of the outer final coil of the hairspring is fixed by a blocking element which is pressed against the free end of the outer final coil of the hairspring by a clamping member, no mechanical torque is transmitted to the hairspring, and therefore the hairspring can be mounted in a rest position in an XY plane parallel to the plane in which the watch movement extends, without any or substantially no effect on its ability to maintain a constant speed. More specifically, it is known that there are substantially no stresses on the free end of the outer final coil of the hairspring perpendicular to the plane in which this free end extends. Another great advantage of the mounting assembly according to the invention lies in the fact that the mounting of the free end of the outer last coil of the balance spring is in no way dependent on the dexterity of the operator performing this mounting operation; therefore, the reproducibility of the operation of a sprung balance assembly equipped with a mounting assembly according to the invention is very remarkable. Effect of the Invention

[0030] Other features and advantages of the present invention will be better understood from a reading of the following detailed description of one embodiment of a mounting assembly according to the invention, said example being given by way of example only with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0031] [Figure 1] FIG. 1 is a top perspective view of an assembly according to the invention, to which the free end of the outer final coil of a hairspring for a timepiece movement is attached. [Diagram 2]FIG. 2 is a bottom perspective view of the mounting assembly according to the present invention shown in FIG. [Diagram 3] FIG. 3 is a top perspective view of a mounting assembly in accordance with the present invention in a separated state. [Figure 4] FIG. 4 is a bottom perspective view of a mounting assembly in accordance with the present invention in a separated state. [Diagram 5] FIG. 5 is a top view of a mounting assembly according to the invention, into which the free end of the outer final coil of a hairspring for a timepiece movement engages. [Figure 6] FIG. 6 is a cross-sectional view of a mounting assembly according to the present invention taken along line VI-VI shown in FIG. [Figure 7] FIG. 7 is a cross-sectional view of a mounting assembly according to the present invention taken along line VII-VII shown in FIG. [Figure 8] FIG. 8 is a top view of a mounting assembly according to the present invention attached to a sprung balance assembly for a timepiece movement. [Figure 9] FIG. 9 is a schematic diagram of a simplified embodiment of a mounting assembly according to the present invention. [Figure 10] FIG. 10 is a top perspective view of a sprung balance assembly provided with a mounting assembly according to the present invention, as shown from the top view of FIG. [Figure 11] FIG. 11 is a bottom perspective view of a sprung balance assembly provided with a mounting assembly according to the present invention, as shown from the top view of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] The invention has arisen from the general inventive idea of ​​mounting the free end of the outer final coil of a timepiece hairspring on a stud by means of a mounting assembly, which fixes it by a combination of mechanical pressing and blocking action. In this way, the free end of the hairspring does not have to be glued to manufacture the mounting part, giving full freedom in the choice of the material used to manufacture the hairspring. Furthermore, since there is no gluing, the mounting assembly according to the invention can be dismantled at any time. Another main advantage of the mounting assembly according to the invention lies in the fact that the free end of the outer final coil of the hairspring is fixed by mechanical clamping and blocking in a direction perpendicular to the plane in which this free end of the hairspring extends. As a result, no mechanical tensile or torsional torques are induced in the free end of the outer final coil of the hairspring by the mounting of this free end of the hairspring, and the speed consistency of the hairspring is not affected by the mounting of the free end of the outer final coil of the hairspring on a stud. This is even more true since the mechanical stresses on the outer final coil of the balance spring in a direction perpendicular to the plane in which it extends are zero or are quite negligible.

[0033] A mounting assembly according to the invention, generally designated by reference numeral 1, is generally shown in Figures 1 and 2 and in particular comprises a stud 2. By way of example only, the stud 2 shown in the drawings is externally bounded by a casing which is generally cylindrical in shape. It is understood that such a stud 2 can have a shape different from a cylindrical shape and can, for example, be a parallelepiped, so that the shape of the stud 2 is not critical for the purposes of the present invention.

[0034] Preferably, but by no means exclusively, a groove 6, preferably of square or rectangular cross section, is formed from the outer wall 4 of the stud 2 towards the inside of the stud 2, as shown in particular in figures 3 and 4. This groove 6 is intended to receive the free end 8 of an outer final coil 10 of a hairspring 12 for a watch movement in order to arrest the hairspring 12, as will be explained in more detail below.

[0035] The mounting assembly 1 according to the invention further comprises a blocking element 14 intended to engage in the groove 6, to come into contact with the free end 8 of the outer final coil 10 of the hairspring 12 and thereafter to press against this free end 8 in order to fix the hairspring 12 in this groove 6.

[0036] For this purpose, the mounting assembly 1 is further supplemented by a clamping member 16 arranged to adjustably press the blocking element 14 against the free end 8 of the outer final coil 10 of the balance spring 12 .

[0037] According to the embodiment of the invention illustrated in the drawings (see, for example, FIG. 3 ), the fastening member 16 may consist of a type of threaded rod 18 provided with a slot head 20. This threaded rod 18 is intended to be screwed into a threaded hole 22 made in the stud 2, which extends into the groove 6 and presses the blocking element 14 against the free end 8 of the outer final coil 10 of the balance spring 12.

[0038] It can be easily seen that, depending on the extent to which the threaded rod 18 is screwed in, the clamping force applied to the free end 8 of the outer final coil 10 of the balance spring 12, via the blocking element 14, and ensuring that this free end 8 is fixed in the groove 6 of the stud 2, can be precisely adjusted.

[0039] The stud 2 may be provided with a friction surface 24, for example a knurl 26. In particular, the friction surface 24 may be used by an operator to better grip the stud 2 when threading the threaded rod 18 into the threaded hole 22 in the stud 2.

[0040] As mentioned above, the fastening member 16 is a threaded rod 18. Of course, this is merely an example and the fastening member 16 could take other forms, such as for example a simple pin that can engage with sufficient grease friction in a hole formed in the stud 2 to press the blocking element 14 firmly against the free end 8 of the outer final coil 10 of the hairspring 12, while being able to be removed from this hole if necessary, for example if the hairspring 12 breaks.

[0041] In a preferred, but non-limiting embodiment, the blocking element 14 is of the type formed by a clamp 28 having a certain elasticity and provided with two generally linear jaws 30a, 30b extending at a distance substantially parallel to each other, the two jaws 30a, 30b being connected to each other at their distal ends 32a, 32b and defining between them a space 34 open towards their proximal ends 36a, 36b.

[0042] In the space 34 open to the proximal ends 36a, 36b of the jaws 30a, 30b, the clamp 28 engages on either side of the wall 38 of the stud 2 resulting from the machining of the groove 6. The mere overlap of the clamp 28 on the wall 38 of the stud 2 is sufficient to hold the clamp 28 in place long enough for the operator to tighten the threaded rod 18. However, this holding force can be slightly increased by providing an inner surface 40 of one of the jaws 30a, 30b of the clamp 28 that extends away from the wall 38 of the stud 2 in the direction of engagement of the clamp 28. The holding force of the clamp 28 on the wall 38 of the stud 2 can be further improved by providing recesses 42a, 42b on the inner surface of the jaws 30a, 30b, whose shape is complementary and matches the shape of the wall 38, allowing the clamp 28 to grip the wall 38 of the stud 2 and hold it securely by friction.

[0043] It is important to understand that the height of the groove 6 is greater than the thickness of the jaws 30a, 30b of the clamp 28, so that when the clamp 28 engages in this groove 6, there is still sufficient space so that the free end 8 of the outer final coil 10 of the balance spring 12 can easily engage in the groove 6.

[0044] The operation of mounting the free end 8 of the outer last coil 10 of the hairspring 12 is carried out as follows: first, the clamp 28 engages on either side of a wall 38 of the stud 2, through a space 34 open to the proximal ends 36a, 36b of the jaws 30a, 30b in the groove 6 of the stud 2. The overlap of the clamp 28 on the wall 38 of the stud 2 is sufficient to ensure that the clamp 28 is held on this wall 38 long enough to mount the free end 8 of the outer last coil 10 of the hairspring 12 on the stud 2. Care is taken to ensure that when the clamp 28 is mounted, a sufficient space 44 remains between the jaws 30a, 30b of the clamp 28 and the back side 46 of the groove 6, so that this clamp 28 is positioned so that it can easily engage with the free end 8 of the outer last coil 10 of the hairspring 12. When the clamp 28 is properly positioned and mounted in the groove 6 of the stud 2, the free end 8 of the outer last coil 10 of the balance spring 12 easily engages in the groove 6 between the back side 46 of the groove 6 and the jaws 30a, 30b of the clamp 28. The free end 8 of the outer last coil 10 of the balance spring 12 often terminates in a plate 50. Depending on the case, this plate 50 is attached to the free end 8 of the outer last coil 10 of the balance spring 12, for example by welding, or is made integral with this free end 8. The guide mark is adjusted by pivoting the mounting assembly 1, in other words by pivoting the mounting point of the outer last coil 10 of the balance spring 12 around the axis 52 of the balance 48, so as to align the impulse pin 54 of the roller 56 with the escapement line 58 (see FIG. 8). For this purpose (see figures 10, 11), the stud 2 engages in an opening 60 made in a stud-holder part 62 supported by a bridge 64, commonly called a cock, and mounted so as to pivot around the staff 52 of the balance 48. Likewise, the groove 6 can very well be made not from outside the stud 2 into the stud 2, but as a through hole 66 in the thickness of the stud 2 (see figure 9). A blocking element 14, for example of the type formed by a rod 68, engages in this through hole 66.Finally, the operator tightens the threaded rod 18 to compress the jaws 30a, 30b of the clamp 28, pressing the clamp 28 against the free end 8 of the outer final coil 10 of the hairspring 12. This completes the operation for mounting the free end 8 of the outer final coil 10 of the hairspring 12, and the hairspring 12 is removably attached to the stud 2.

[0045] It goes without saying that the invention is not limited to the above described embodiment, and that the skilled person can think of various simple alternatives and modifications without departing from the scope of the invention as defined by the appended claims. In particular, it is understood that the groove 6 can have a cross section that is not square or rectangular. It is also noted that the friction surface 24, such as the knurling 26, provided on the stud 2 is particularly useful after the stud 2 has been driven into the stud holder part 62. More specifically, the threaded rod 18 can be screwed into the locked position with relative ease. The only thing that can turn the stud 2 during this operation is the friction induced by the thread of the threaded rod 18 in the threaded hole of the stud 2. However, at this stage of the operation, this friction is negligible, taking into account the torque required to turn the stud 2. However, once the threaded rod 18 reaches the blocking position inside the threaded hole 22, a large part of the tightening torque transmitted by the operator to the threaded rod 18 is transmitted to the stud 2, which can cause the stud 2 to turn relative to the stud holder part 62. Needless to say, such turning must be avoided. For this purpose, the stud 2 is provided with a knurl 26, which has the effect of increasing the resistance of the stud 2 to this torque, for example by contact with the stud holder part 62. It should also be understood that, depending on the geometry of the hairspring 12, this hairspring 12 can engage in the groove 6 of the stud 2 at a point along its length different from the length of the free end 8 of its outer final coil 10. It should also be understood that the free end 8 of the outer final coil 10 of the hairspring 12 is fixed by mechanical clamping and blocking in a direction perpendicular to the plane in which the free end 8 of the hairspring 12 extends. If the hairspring 12 terminates in a plate 50, which extends parallel to the plane in which the hairspring 12 lies, the clamping-blocking of this plate 50 takes place perpendicular to the plane of the hairspring 12. Conversely, if the plate 50 extends perpendicular to the plane in which the balance spring 12 lies, the clamping-blocking of this plate 50 takes place in a direction parallel to the plane of the balance spring 12 .In other words, the threaded rod 18 is screwed onto the stud 2 in a direction perpendicular to the longitudinal axis of symmetry of the stud 2. It should also be noted that since the hairspring 12 takes the form of a very thin ribbon wound around itself in a series of coils, the plane in which the free end 8 of the outer final coil 10 of the hairspring 12 extends is understood to mean the plane in which this winding lies. It should also be noted that the plate 50 is a surface element, for example of rectangular shape, which, depending on the case, lies either in the plane of the hairspring 12 or perpendicular to this plane. [Explanation of symbols]

[0046] 1 Mounting Assembly 2 Studs 4. Exterior Wall 6 grooves 8 free end 10 Outer final coil 12 Hairspring 14 Blocking Elements 16 Fastening member 18 Threaded Rod 20 Slot Head 22 screw holes 24 Friction surface 26 Knurling 28 Clamp 30a, 30b Joe 32a, 32b distal end 34 Space 36a, 36b proximal end 38 Wall 40 sides 42a, 42b Recess 44 Space 46 Bottom 48 Temp 50 Plates 52 Staff 54 Impulse pin 56 Lola 58 Escape Line 60 Rectangular opening 62 Stud holder part 64 Bar 66 Through hole 68 Rod

Claims

1. A mounting assembly (1) for mounting a free end (8) of an outer final coil (10) of a hairspring (12) for a timepiece movement, said mounting assembly (1) comprising a stud (2) and a blocking element (14), said stud (2) being provided with a groove (6) which engages said hairspring (12) along its length, said blocking element (14) also engaging in said groove (6) and in contact with said hairspring (12), said mounting assembly (1) further comprising a clamping member (16) which presses said blocking element (14) against said hairspring (12) in a direction (Z) perpendicular to a plane in which the windings of the outer final coil lie.

2. 2. A mounting assembly (1) according to claim 1, characterized in that the balance spring (12) meshes in the groove (6) of the stud (2) via the free end (8) of its outer final coil (10).

3. 3. A mounting assembly (1) according to claim 2, characterized in that the free end (8) of the outer final coil (10) of the balance spring (12) is fixed by mechanical clamping and blocking in a direction perpendicular to the plane in which this free end (8) of the balance spring (12) extends.

4. 2. A mounting assembly (1) according to claim 1, characterized in that the groove (6) extends inwards from an outer wall (4) of the stud (2), the outer wall (4) being provided on a side along a longitudinal direction of the stud (2), the longitudinal direction of the stud (2) being perpendicular to the plane of the balance spring (12).

5. 5. A mounting assembly (1) according to claim 4, characterized in that the groove (6) has a height and a thickness such that once the blocking element (14) engages in this groove (6), there remains sufficient space in the groove (6) to allow the free end (8) of the outer final coil (10) of the balance spring (12) to engage therein, said height being measured in a direction joining the two ends of the opposing inner walls of the groove (6).

6. The space into which the free end (8) of the outer final coil (10) of the hairspring (12) is engaged extends between the blocking element (14) and one side (46) of the groove (6), said one side (46) being the bottom side of the stud. A mounting assembly (1) according to claim 5, characterised in that

7. 7. A mounting assembly (1) according to claim 6, characterized in that the free end (8) of the outer final coil (10) of the balance spring (12) terminates in a plate (50) attached to or made integral with said free end (8).

8. 2. A mounting assembly (1) according to claim 1, characterized in that a hole (22) into which the fastening member (16) engages is formed in the stud (2) such that the fastening member (16) extends into the groove (6) and presses against the blocking element (14), pressing the blocking element against the free end (8) of the outer end coil (10) of the hairspring (12).

9. 9. A mounting assembly (1) according to claim 8, characterized in that the fastening member (16) is a threaded rod (18) and the hole (22) is threaded.

10. 9. A mounting assembly (1) according to claim 8, characterized in that the blocking element (14) is a clamp (28) provided with two jaws (30a, 30b) connected to each other at their distal ends (32a, 32b), the two jaws (30a, 30b) defining between them a space (34) open towards their proximal ends (36a, 36b).

11. A mounting assembly (1) according to claim 10, characterized in that the stud (2) comprises a wall (38) which bounds the groove (6), the wall (38) being a rear surface of the groove (6).

12. 12. A mounting assembly (1) as claimed in claim 11, characterized in that an inner surface of one of the jaws (30a, 30b) of the clamp (28) has a surface (40) that extends away from the wall (38) of the stud (2) in a direction of engagement of the clamp (28) on the stud (2), the direction of engagement of the clamp (28) being the direction of extension of the jaws (30a, 30b).

13. 12. A mounting assembly (1) as set forth in claim 11, characterized in that the inner surfaces of the jaws (30a, 30b) of the clamp (28) are provided with recesses (42a, 42b) whose shape is complementary to and matches the shape of the wall (38) and enables the clamp (28) to grip and hold the wall (38).

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