CLOCK ORDER WITH A RUSH AND A RUSH WAVE

Description

technical field

[0001] The present invention relates to the field of watchmaking. More particularly, it relates to a watch assembly comprising: a balance shaft having a first annular rim defining a first axial stop, a first bearing of diameter D adjoining the first rim, a balance wheel, comprising a hub having a central opening, through which the balance wheel is adjusted on the first bearing, supported on the first axial stop, a locking member, rigidly mounted on the balance shaft and arranged to lock the balance wheel against the annular rim. State of the art

[0002] Typically, the balance wheels are driven onto a lip of the balance shaft. This lip forms a stop, against which the balance wheel comes to rest.

[0003] The balance wheels are machined from metal bars by turning. The materials used, both for the balance wheel and the balance staff, allow for dimensional accuracy and controlled extrusion forces.

[0004] It is known that parts made of silicon cannot withstand the stresses of pressing, due to their fragility caused by the absence of a plastic domain in silicon.

[0005] For wheels or spirals made of silicon, the issue of fastening has already been addressed. One solution proposed is to use an intermediate sleeve between the shaft and the silicon component to absorb the thrust forces. However, maintaining centering during deformation is not easy.

[0006] It was proposed to rivet the silicon part by deforming a lip formed on the shaft to fold it over the silicon part. While this solution is relatively practical at the end of the shaft, it presents other difficulties, particularly in terms of precision, when components need to be mounted on the shaft, on the folded lip.

[0007] Numerous solutions have been described for creating elastic structures at the midpoint of the silicon component to clamp it onto the shaft. However, these solutions are difficult to apply for mounting a balance wheel due to its mass and the inertial effects it experiences. Indeed, the friction generated by the elastic pressure remains low and may be insufficient to hold a balance wheel, for example, in the event of shocks. Document EP 2860591 A1 relates to a watch assembly with a shaft, a balance wheel, and a locking element. Document JPS5181907A relates to a watch assembly with a shaft, a magnet surrounded by flanges, and a leaf spring.

[0008] The present invention therefore aims to provide a solution for assembling a balance wheel, particularly a balance wheel whose hub is made of a fragile material, such as silicon. Disclosure of the invention

[0009] More specifically, the invention relates to a watch assembly as mentioned above and comprising, a balance staff, a balance wheel and a locking member, said locking member having a concavity or clearance in its part located around the staff, which limits the contact between the locking member and the balance wheel to an area located around an annular portion, surrounding the staff.

[0010] According to the invention, the shaft has a second annular rim, defining a second axial stop, a second bearing surface of diameter d, with D>d, adjoining the second rim, and such that the locking member is driven into a stop on the second rim.

[0011] Advantageously, the locking element is annular in shape, with a central opening sized to allow for driving onto the shaft at diameter d.

[0012] Preferably, once assembled, the locking element is elastically deformed.

[0013] In one variant, the balance wheel is made at least partially of a brittle material, meaning one that does not undergo plastic deformation when fracture occurs, or has an elongation (A%) before fracture of less than 0.2% or zero when measured during a tensile test, at least in the area surrounding an annular portion. Thus, the balance wheel hub can be silicon-based.

[0014] In yet another preferred variant, the tree has a proximal puncture, on the first edge.

[0015] Advantageously, the central opening of the balance wheel hub and the first rim can have corresponding geometries, defining a non-circular form and counter-form pair. Brief description of the drawings

[0016] Further details of the invention will become clearer upon reading the following description, made with reference to the attached drawing in which: there figure 1is an isometric view of a watch assembly according to the invention, the figure 2 is a cross-sectional view showing the assembly of the components forming the whole represented on the figure 1 , and the figure 3 is a schematic cross-sectional representation of a portion of the locking mechanism. Method of embodiment of the invention

[0017] We have represented on the figure 1 , a watch assembly comprising a balance shaft 10, a balance wheel 20 and a locking device 30 for the balance wheel 20 on the shaft 10. Such a watch assembly is intended to be associated with an elastic return device, typically a balance spring, to form a resonator of a watch movement.

[0018] More specifically, the balance shaft 10 has a first annular rim 11 defining a first axial stop. This first rim 11 can be relatively wide and take the form of an annular plate. To be sufficiently rigid without adding too much weight to the balance shaft 10, the rim can be extended by a conical portion 12 which connects to the cylindrical part of the shaft 10.

[0019] A first bearing surface 13 of diameter D is adjacent to the first flange 11. It is designed to receive the balance wheel 20, as described below. Advantageously, a pin 14 is located on the first flange 11, at the junction between the first flange 11 and the first bearing surface 13. In other words, the shaft 10 has a proximal pin 14 on the first flange 11. This avoids any risk related to an imprecise junction between the first flange 11 and the first bearing surface 13, which could hinder the positioning of the balance wheel 20.

[0020] The balance wheel 20 has a hub 22 with a central opening, through which the balance wheel 20 is adjusted on the first bearing 13, resting on the first rim 11. By adjusted, we mean a positioning without constraint, but with a minimum play to allow free positioning on the first rim 11. The central opening and the first bearing 13 can be circular in shape.

[0021] The locking member 30 is rigidly mounted on the balance shaft 10 and is arranged to lock the balance wheel 20 against the first annular flange 11. The locking member 30 is typically pressed onto the shaft 10. To achieve this, the shaft 10 has a second annular flange 15, defining a second axial stop, a second bearing surface 16 of diameter d, with D > d, adjacent to the second flange. The locking member 30 includes an opening 32, typically circular and central, sized to allow pressing onto the shaft 10 at diameter d. The locking member 30 is pressed against the second annular flange 15.

[0022] According to an important aspect of the invention, the locking member 30 has a concavity in its part located around the opening 32 and the shaft 10, which limits the contact between the locking member 30 and the balance wheel 20 to an area located around an annular portion, surrounding the shaft 10. In other words, in this annular portion of the balance wheel 20 and more particularly in an annular portion of the hub 22 surrounding the central opening, there is no contact between the locking member 30 and the balance wheel 20.

[0023] In a preferred embodiment, the locking member 30 is elastically deformable and is of the Belleville washer type. In other words, it is a conical ring with a central opening 32 for the passage of the shaft 10. More generally, the locking member 30 may be an annular piece with a concavity, either circular or centrally symmetric. The concavity is oriented towards the first rim. Without departing from the invention, the contact between the locking member 30 and the balance wheel 20 may not be continuous, for example, with interruptions in the annular wall of the locking member 30, forming arms. These arms may, for example, bear against the arms of the balance wheel 20, connecting the hub 22 and the rim. The arms can optionally cooperate with stopping structures formed in the balance wheel in order to make the locking member 30 and the balance wheel 20 rotationally fixed.

[0024] Advantageously, during its insertion onto the shaft 10, the locking member 30 is elastically deformed under the effect of the pressure exerted on the rocker arm 20 and the reaction force exerted on the locking member 30. The rocker arm 20 is thus held against the first flange 11.

[0025] Thus, the locking member 30, in its rest state, i.e. without deformation, has a gap Δh between the portion 34 intended to be pressed against the second annular rim 15 of the shaft 10 and the portion 36 intended to be pressed against the rocker arm 20 ( figure 3 ). Δh is greater than the difference between, on the one hand, the height dh between the first rim 11 and the second rim 15 and, on the other hand, the thickness e of the balance wheel 20, at the level of the support of the locking member 30.

[0026] Therefore, Δh > dh - e.

[0027] Thus, when the locking member 30 is driven onto the shaft 10, it is elastically deformed. By controlling and managing the dimensions of the first and second flanges 11, on the one hand, and the thickness of the balance wheel 20, on the other, as well as by controlling the geometry of the locking member 30, the clamping force exerted on the balance wheel 20 by the locking member 30 can be advantageously guaranteed. Once the locking member 30 comes to rest against the second flange, the clamping force is independent of the driving force exerted by the locking member 30.

[0028] Preferably, the balance wheel 20 is made of a material that does not plastic deformation, at least at the hub 22 and the arms. More specifically, the balance wheel 20 is made of a material that does not plastic deformation, at least in the contact area between the locking member 30 and the balance wheel 20, as defined above. This material that does not plastic deformation is advantageously silicon or a silicon-based material, which allows, by manufacturing this component from a wafer or plate, precise control of the thickness e.

[0029] The embodiment described above includes a hub 22 with a circular opening, and a first flange 11 of corresponding shape. Alternatively, a non-circular form and counter-form pair can be provided on the rocker arm 20 and on the shaft 30 to eliminate the degree of relative rotational freedom between these two parts when the rocker arm 20 rests on the first flange 11. This can be achieved by a flat surface, a finger or lug, or a polygonal structure such as a triangle, a square, or another n-sided polygon, the polygon being able to be regular, with n typically going up to 10. The clamping force of the locking member 30 can then be limited to axial retention.

[0030] In one variant, structuring or microstructuring can be performed at the interface between the locking member 30 and the balance wheel 20. Advantageously, the structuring or microstructuring is carried out on the balance wheel, preferably made of silicon. Silicon can be chemically or plasma-structured, or even by applying a mask to select the areas to be structured. Alternatively, structuring can also be performed, for example by a mechanical treatment such as grinding, on the interface of the locking member 20. This increases the coefficient of friction between the balance wheel and the locking member and improves the balance wheel's stability, particularly during rotation, relative to the locking member.

Claims

1. Horological assembly comprising: ∘ a balance staff (10) provided with a first annular rim (11) defining a first axial abutment, a first bearing surface (13) of diameter D adjoining the first annular rim (11), ∘ a balance (20), comprising a hub (22) provided with a central opening, through which the balance (20) is fitted on the first bearing surface (13), resting on the first axial abutment, ∘ a locking member (30), rigidly mounted on the balance staff (10) and arranged to lock the balance (20) against the annular rim, the locking member (30) having a concavity in its portion located around the staff (10), which limits the contact between the locking member (30) and the balance (20) to a zone located around an annular portion, surrounding the staff (10), characterized in that the staff (10) has a second annular rim (15), defining a second axial abutment, a second bearing surface (16) of diameter d, with D>d, adjoining the second rim, and in that the locking member (30) is press-fitted in abutment on the second rim.

2. Horological assembly according to the preceding claim, characterized in that the locking member (30) is of annular shape, with a central opening dimensioned to allow press-fitting on the staff (10).

3. Horological assembly according to one of the preceding claims, characterized in that the locking member (30) is elastically deformed.

4. Horological assembly according to one of the preceding claims, characterized in that the balance (20) is made at least partially of a brittle material, without plastic deformation at rupture, at least at the level of said zone located around an annular portion.

5. Horological assembly according to claim 4, characterized in that said hub (22) of the balance (20) is silicon-based.

6. Horological assembly according to one of the preceding claims, characterized in that the staff (10) has a proximal recess (14), on said first annular rim (11).

7. Horological assembly according to one of the preceding claims, characterized in that the central opening of the hub (22) of the balance (20) and the first annular rim (11) have corresponding geometries, defining a non-circular shape and counter-shape pair.