CH720294A2 - Assembly comprising a balance spring and a pin and timepiece comprising such an assembly - Google Patents

Abstract

The invention relates to an assembly comprising a hairspring (20) and a pin, said hairspring (20) and said eyepiece being intended to be assembled to one another, said hairspring comprising, in the vicinity of its external end, a securing member. stop (20.2), said pin comprising: – a stopping structure arranged to limit all the degrees of freedom of the stop member (20.2) in the plane of said spiral by cooperating with said stop member, and – at least one deformable structure and occupying before deformation a state allowing the stop member (20.2) to be placed in the stopping structure, and capable of being deformed to occupy a second state in which the degrees of freedom of the stop member (20.2 ) outside the plane of the hairspring, are deleted.

Description

Technical area

[0001] The present invention relates to the field of watchmaking and more particularly concerns an assembly comprising a hairspring and a pin, both of which are adapted to cooperate together. The invention also relates to a hairspring assembled to said pin.

State of the art

[0002] The resonator of a mechanical timepiece comprises, in its most common embodiment, a balance wheel coupled to a hairspring. The latter ensures the elastic return of the balance and generally comprises a central end secured to the balance shaft which pivots, and a distal end, secured to a fixed frame of reference. Still in a classic case, the frame of reference is a part of the frame, called a cock or balance bridge, and the distal end is fixed to it by means of a eyebolt. The eyebolt can also be placed in a mobile eyebolt holder, in order to adjust the position of the external attachment point of the hairspring.

[0003] The hairspring is generally fixed in a hole in the piton by means of a conical pin and, with careful work, so that the hairspring is not deformed, that is to say arched in the direction of its height by the rounding of the pin, a flat surface is made on it which presses against the blade of the hairspring and also allows, before forcing the pin, to properly orient said blade in the pin so as not to be obliged to twist it to lay the hairspring flat.

[0004] This way of doing things has many disadvantages. Firstly, it does not make it possible to reduce the size of the pin because it must, on the one hand, be large enough to accommodate the hole for the balance spring and, on the other hand, be made of a metal having a resistance large enough for traction and whose density is high enough, otherwise it does not support the force of pinning the hairspring. Furthermore, when it comes to weak hairsprings for small parts, it is difficult to get the pin to protrude little or not beyond the eyebolt, which greatly facilitates centering and flattening the hairspring because we can then grab it near its entrance into the piton. Knowing also that the operation of centering and flattening the hairspring on the ferrule, as well as aligning the eyebolt in relation to the balance wheel, is all the easier as the eyebolt is lighter, it is therefore to all importance of seeking to eliminate all the causes which oblige it to be chosen large and heavy compared to the hairspring.

[0005] If the hairsprings have historically been made from metal alloys, they are currently also made from silicon, in particular in order to reduce the sensitivity of the resonator to magnetic fields. Silicon is a material that is certainly elastic, but fragile and brittle. In fact, it does not cope well with the constraints linked to the fixing methods of the prior art, typically, the pinning mentioned above.

[0006] Thus, the silicon hairsprings are usually glued to the pin or pinched in relatively complex systems. However, according to certain regulations, in particular those which define the attribution of the Geneva hallmark, it is not authorized to assemble elements by gluing.

[0007] The present invention aims to propose an alternative method, making it possible to fix the external end of hairsprings, in particular made of silicon, without applying excessive stresses to the hairspring and without using gluing.

Disclosure of the invention

[0008] More precisely, the invention relates to an assembly comprising a hairspring and a pin, said hairspring and said pin being intended to be assembled to one another, said hairspring comprising, in the vicinity of its external end, a stop member, said pin 10 comprising: – a reception zone comprising a stopping structure arranged to limit or block all the degrees of freedom of the stop member in the plane of said hairspring by cooperating with said stop member, and – at least one deformable structure and occupying before deformation a state (for example a first state) making it possible to arrange, arrange or accommodate the stop member in the stopping structure, and capable of being deformed to occupy a second state in which the degrees of freedom of the stop member outside the plane of the hairspring are eliminated or blocked.

[0009] The degrees of freedom in the plane of the hairspring can include two translations perpendicular to each other and included in the plane of the hairspring, and a rotation around an axis normal to the plane of the hairspring. The degrees of freedom outside the plane of the hairspring can include a translation along an axis normal to the plane of the hairspring, and two rotations each around an axis contained in the plane of the hairspring and perpendicular to the axis of the other rotation.

The assembly according to the invention may comprise one or other of the following characteristics, possibly in combination if they are compatible with each other: – the stopping structure and the stop member are of complementary shapes, – the stopping structure is elastically deformable, – the stopping structure is plastically deformable, – the stopping structure and the deformable structure comprise a plurality of studs and the deformable structure comprises a plurality of claws, a claw surmounting a stud , – the deformable structure is made of gold, – the deformable structure and the stopping structure are made of gold, – the eyebolt is made of gold, – the hairspring is made of silicon, – the stop member forms a cross with the hairspring, in the plane of the hairspring.

[0011] The invention also relates to a timepiece comprising an assembly comprising a hairspring and a peg, as mentioned above, in which the stop member of said hairspring is arranged in said reception zone of said peg, said peg and said spiral being joined to each other by plastic deformation of the deformable structure.

Brief description of the drawings

[0012] Other details of the invention will appear more clearly on reading the description which follows, made with reference to the appended drawing in which: – Figure 1 is a view of a piton forming part of a spiral assembly -bolt according to a particular embodiment of the invention, and – Figure 2 is a view of the same eyebolt, with a spiral adapted to cooperate with this eyebolt.

Mode of carrying out the invention

[0013] Figure 1 shows a piton 10 intended to form part of a spiral-piton assembly according to the invention. The eyebolt 10 is intended to be positioned in a eyebolt carrier or in a bridge, not shown.

[0014] It includes a non-circular base 10.2, in the example it is a circular base truncated by two parallel edges. This geometry makes it possible to angularly index the eyebolt 10 in the eyebolt carrier. Other indexing solutions are possible, for example by providing a housing at the base of the eyebolt carrier, which can cooperate with a corresponding shape of the eyebolt carrier or the bridge.

[0015] The pin 10 comprises a reception zone 10.4 intended to receive a portion close to the outer end of the hairspring 20. This reception zone 10.4 is located on the free side of the pin 10, when the latter is mounted in the door -piton or in the cock.

[0016] The reception zone 10.4 comprises a stopping structure 10.6 arranged to cooperate with the hairspring 20 to limit all the degrees of freedom in the plane of said hairspring, of the portion of the hairspring housed in the pin 10. This structure of stop 10.6 has physical stops, capable of cooperating with the hairspring.

[0017] The hairspring 20 comprises, in the vicinity of its external end, a stop member 20.2, shaped to cooperate with the stopping structure 10.6, to limit all the degrees of freedom in the plane of said hairspring, of the stop member 20.2.

[0018] In the example illustrated, the stop structure 10.6 and the stop member 20.2 are of complementary shapes. More particularly, the stop member 20.2 has a bar 20.4 arranged transversely with respect to the last turn and it forms a cross with the hairspring 20, in the plane of the latter. The pin 10 comprises, at the level of the reception zone 10.4, a plurality of studs 10.8, defining between them grooves 10.10 which form a hollow cross, in which the cross-shaped stop member 20.2 of the hairspring can be placed. The relative dimensioning of the stopping structure 10.6 and the stop member 20.2 leaves a slight play allowing effortless, but nevertheless precise, positioning. A clearance of around 0.02 mm can typically be expected.

[0019] Different variants can be provided to ensure the positioning of the end of the hairspring 20 on the pin 10. For example, the stop member 20.2 can be a cavity or a housing formed in the hairspring 20 in which it can take place a stopping structure 10.6 projecting relative to the reference surface of the reception zone 10.4 of the piton 10. A reverse arrangement is also possible. At least two pairs of hollow/protruding elements can be provided to avoid rotation of the end of the hairspring during assembly, or non-circular geometries can be provided.

Alternatively, it is also possible to have a notch on the edge of the grooves 10.10 defined by the studs 10.8, with a corresponding notch in the vertical walls of the hairspring 20.

[0021] The fact of limiting all the degrees of freedom of the end of the hairspring in the plane allows the end of the hairspring to be precisely positioned during its assembly to the pin 10, as will be seen below, including in mastering its active length.

It will be noted that if the stopping structure is in the main plane of the turns of the hairspring, it includes an opening or a passage allowing the last turn of the hairspring to be placed there.

[0023] Thus, when the stop member 20.2 is positioned in the reception zone, in cooperation with the stopping structure, it can possibly be removed along the z axis. However, to be used, the balance spring 20 must be fixed and the remaining degrees of freedom must be eliminated (in particular translation and out-of-plane bending).

[0024] To do this, the piton 10 comprises at least one deformable structure 10.12, plastically deformable according to a first variant, and occupying before deformation a state allowing the stop member 20.2 to be placed in the stopping structure 10.6, and suitable to be deformed to occupy a second state in which the degrees of freedom of the stop member 20.2 outside the plane of the hairspring are eliminated.

[0025] The deformable structure 10.12 comprises claws or lugs 10.14, capable of being deformed by a rivet or equivalent and forming ribs enveloping or at least partially covering the spiral 20, all degrees of freedom of the portion comprising the deformable member. stop, then being deleted.

[0026] In the embodiment illustrated in the drawing, the claws 10.14 are each arranged on one of the pads 10.8 of the stopping structure 10.6. Advantageously, this configuration makes it possible to have the claws 10.14 as close as possible to the hairspring. In this configuration, the height of the stopping structure 10.6 is substantially equal to the height (dimension orthogonal to the plane of the hairspring) of the hairspring. The height of the stopping structure 10.6 can also be less than that of the hairspring, the base of the claws then being in the plane of the hairspring.

Other variants can be provided, depending on the geometries chosen for the stop structure 10.6, in which the deformable structure 10.12 overcomes the stop structure, in other words, the deformable structure is arranged on the structure of stop. If the respective structures are formed of several elements, stopping elements and deformable elements, then the elements can form a pair of a stopping element with a deformable element, as in the example illustrated (a stud associated with a claw ). We could also have several deformable elements arranged on a stopping structure. In the case where the stop structure is a projecting finger, and the stop structure is a cavity formed in the hairspring, then the deformable structure can be dissociated from the stop structure.

[0028] Preferably but not restrictively, the hairspring is made of silicon, which makes it possible to engrave various shapes to produce the stopping structure. Silicon being fragile and capable of being damaged by excessive compression, we can advantageously choose to make the deformable structure in a material which is soft, that is to say deformable without having to apply a significant force on the rivet. The hardness of the material from which the piton is made is advantageously less than 250HV, more advantageously less than 200HV. The silicon hairspring may have any crystalline nature, be monocrystalline, of any crystalline orientation, or be polycrystalline. It may be coated with oxide or another thermal compensation layer.

[0029] Thus, the deformable structure can be made of gold or a gold alloy. Other materials may be suitable, such as copper-based alloys, brass, nickel silver and bronze. The force exerted for riveting the hairspring is limited and the stress suffered by the hairspring can thus be reduced. The deformable structure can be attached to the peg 10 or to the stopping structure. We can also plan to make the deformable structure and the stopping structure in gold, or to make the entire piton 10 in gold.

[0030] The shape of the claws and their section in particular can be chosen by those skilled in the art so as to adjust the riveting force necessary for their deformation.

[0031] In a variant, it is possible for the deformable structure to be elastically deformable. Similar to what has been described above, the deformable structure is able to occupy before deformation a state allowing the stop to be placed in the stopping structure, and able to be deformed to occupy a second state in which the degrees of freedom of the stop member outside the plane of the hairspring, are eliminated.

[0032] To maintain the deformable structure in the deformed state, that is to say also hold the end of the hairspring in place in the pin 10, a locking member can be fixed on the pin 10, so as to constrain the deformable structure in its deformed state. For example, the locking member can be a cover which overcomes the deformable structure, the cover comprising tongues provided with a notch, which cooperates with a rack arranged on the wall of the pin 10. It is thus possible to adjust the tightening and the support provided by the cover, by adjusting the position along the z axis, of the cover on the peg 10.

Alternatively, the elastically deformable structure can allow direct clipping of the stop member in the deformable structure. In other words, the engagement of the stop member in the deformable structure causes the elastic deformation of the latter. When the stop member is positioned in the stopping structure, the deformable structure elastically returns to its non-deformed state, which provides a clipping effect for the hairspring.

Another aspect of the invention relates to a timepiece comprising a set of a hairspring and a pin 10 as described above, fixed to each other. The abutment member of the hairspring is arranged in the receiving zone of said peg 10, said peg 10 and said hairspring being secured to each other by the deformable structure. In the case of a plastically deformable structure, the structure being deformed, the claws form ribs enveloping or at least partially covering the hairspring.

[0035] The invention can be applied not only to silicon hairsprings, but more generally to hairsprings made from brittle materials, such as glasses, of the Zerodur type, or hairsprings made from composite materials, based on carbon nanotubes.

Claims (11)

1. Assembly comprising a hairspring (20) and a pin (10), said hairspring (20) and said pin (10) being intended to be assembled to one another, said hairspring comprising, near its external end, a stop member (20.2), said pin (10) comprising – a stopping structure (10.6) arranged to block all the degrees of freedom of the stop member (20.2) in the plane of said spiral by cooperating with said stop member, and – at least one deformable structure (10.12) and occupying before deformation a state allowing the stop member (20.2) to be placed in the stopping structure (10.6), and capable of being deformed to occupy a second state in which the degrees of freedom of the stop member (20.2) outside the plane of the hairspring, are blocked. 2. Assembly according to claim 1, characterized in that the stopping structure (10.6) and the stop member (20.2) are of complementary shapes. 3. Assembly according to one of the preceding claims, characterized in that the stopping structure (10.6) is elastically deformable. 4. Assembly according to one of claims 1 and 2, characterized in that the stopping structure (10.6) is plastically deformable. 5. Assembly according to claim 4, characterized in that the stopping structure (10.6) and the deformable structure (10.12) comprise a plurality of studs (10.8) and in that the deformable structure (10.12) comprises a plurality of claws (10.14), each claw surmounting a stud. 6. Assembly according to one of claims 4 and 5, characterized in that the deformable structure (10.12) is made of gold. 7. Assembly according to claim 6, characterized in that the deformable structure (10.6) and the stopping structure (10.12) are made of gold or a gold alloy. 8. Assembly according to claim 7, characterized in that the pin (10) is made of gold or a gold alloy. 9. Assembly according to one of the preceding claims, characterized in that the spiral (20) is based on silicon. 10. Assembly according to one of the preceding claims, characterized in that the stop member (20.2) forms a cross with the hairspring, in the plane of the hairspring. 11. Timepiece comprising an assembly according to one of claims 1 to 10, in which the stop member (20.2) of said hairspring is disposed in said reception zone of said pin (10), said pin (10) and said hairspring being secured to one another by plastic deformation of the deformable structure.