EP3839656B1 - Horological balance - Google Patents

Description

Field of the invention

The invention relates to a balance wheel for a watch movement, comprising rigid parts constituted by a hub defining the pivot axis of the balance wheel, a rim, and at least one arm connecting the rim to the hub, and comprising at least one member of holding for receiving and pinching in position a rod of a weight.

The invention relates to the field of watchmaking oscillators, and more particularly to the field of balance wheels comprising inertia adjustment and/or balancing means.

Background of the invention

Numerous creations of balance wheels with inertia adjustment and/or balancing means are known. In particular, we know of balances with weights screwed or driven into installations of the serge of a balance. Certain achievements have attempted to ensure the maintenance of weights by pinching. We thus know the document CH 705 238 or the document FR 3 043 801 , which each disclose a balance comprising at least one slot for receiving and pinching in position a rod of a flyweight, the slot being delimited by, on the one hand a said rigid part of the balance, and on the other hand an elastic arm permanently recalled towards said rigid part of said balance defining said slot to maintain the flyweight.

When inserting the weights, the elastic arm undergoes significant plastic deformations due to its spacing. These plastic deformations can then cause defects in the material, such as cracks. This can therefore harm the reliability of the balance wheel, or even damage it, as the weight may no longer be held correctly by the elastic arm and become dislodged.

Summary of the invention

The invention aims in particular to overcome the various disadvantages of these known techniques.

More precisely, an objective of the invention is to provide a balance wheel making it possible to obtain better support of the weights with an elastic arm capable of remaining in stress levels not exceeding its elastic limit and thus minimizing the risk of defects.

Another objective of the invention is to provide a balance wheel with an elastic arm having a sufficiently rigid geometry and allowing sufficient support force to allow the weight to be held in place regardless of the type of shock that the watch experiences. suddenly.

These objectives, as well as others which will appear more clearly later, are achieved according to the invention using a balance wheel for a clock movement according to claim 1.

• l'extrémité distale libre du bras élastique présente un méplat, le méplat étant disposé en vis-à-vis de la partie du balancier présentant une rigidité supérieure ou égale à celle du bras élastique ;
• le bras élastique comprend une section constante sur un angle β, au centre du cercle de centre C, supérieur à 150° ;
• le méplat s'étend sur un angle γ, au centre du cercle de centre C, compris entre 20° et 50° ;
• la fente s'étend parallèlement à une radiale issue dudit axe de pivotement ;
• le bras élastique est conformé pour rester sous un seuil de déformation plastique de 0.3% en fond de logement lors d'une élévation sensiblement verticale du bras élastique par rapport à la partie rigide du balancier pour mettre en place la tige de la masselotte ;
• le logement est de forme circulaire avec une entrée définie par la fente et un fond, le fond du logement présentant des dimensions supérieures à l'entrée du logement ;
• le bras élastique fourni une force de maintien d'au moins 0.7N ;
• la partie rigide comprend une encoche pour positionner la masselotte, la largeur de l'ouverture étant inférieure au diamètre de la tige de la masselotte ;
• le bras élastique est solidaire de la serge ;
• le bras élastique est solidaire du moyeu ;
• l'au moins un bras élastique est monobloc avec le balancier ;
• le balancier comprend plusieurs bras élastiques, les bras élastiques étant disposés selon une symétrie centrale ayant pour centre celui du balancier.

In accordance with other advantageous variants of the invention:

• the free distal end of the elastic arm has a flat surface, the flat surface being arranged opposite the part of the balance wheel having a rigidity greater than or equal to that of the elastic arm;
• the elastic arm comprises a constant section over an angle β, at the center of the circle with center C, greater than 150°;
• the flat area extends over an angle γ, at the center of the circle with center C, between 20° and 50°;
• the slot extends parallel to a radial coming from said pivot axis;
• the elastic arm is shaped to remain under a plastic deformation threshold of 0.3% at the bottom of the housing during a substantially vertical elevation of the elastic arm relative to the rigid part of the balance to position the flyweight rod;
• the housing is circular in shape with an entrance defined by the slot and a bottom, the bottom of the housing having dimensions greater than the entrance to the housing;
• the elastic arm provides a holding force of at least 0.7N;
• the rigid part includes a notch for positioning the flyweight, the width of the opening being less than the diameter of the rod of the flyweight;
• the elastic arm is integral with the serge;
• the elastic arm is integral with the hub;
• the at least one elastic arm is in one piece with the balance;
• the balance wheel comprises several elastic arms, the elastic arms being arranged in central symmetry having as center that of the balance wheel.

The invention also relates to a watch movement comprising a balance-spring oscillator system conforming to the invention.

The invention also relates to a timepiece comprising a watch movement according to the invention.

The invention also relates to a method of mounting a weight on a balance wheel according to the invention.

Thus, the object of the present invention, through its various functional and structural aspects described above, makes it possible to obtain a more robust balance wheel in particular thanks to the disappearance of surface tensile stress along the interior surface of the elastic arm , this making it possible to limit the formation of weakened zones.

Summary description of the drawings

• la figure 1 est une vue de dessus d'un balancier conforme à l'invention selon un premier mode de réalisation ;
• la figure 2 est une vue de dessus d'un organe de serrage élastique d'un balancier conforme à l'invention selon un premier mode de réalisation ;
• la figure 3 est une vue de dessus d'un balancier conforme à l'invention selon un second mode de réalisation ;
• les figures 4a et4b illustrent des masselottes pouvant équiper un balancier conforme à l'invention.

Other characteristics and advantages of the invention will appear more clearly on reading the following description of a particular embodiment of the invention, given by way of simple illustrative and non-limiting example, and the appended figures, among which :

• there figure 1 is a top view of a balance according to the invention according to a first embodiment;
• there figure 2 is a top view of an elastic clamping member of a balance wheel according to the invention according to a first embodiment;
• there Figure 3 is a top view of a balance according to the invention according to a second embodiment;
• THE figures 4a And 4b illustrate weights which can be fitted to a balance according to the invention.

Detailed description of the preferred embodiments

A balance wheel according to an exemplary embodiment will now be described in the following, referring jointly to the figures 1, 2 , 3 , 4a and 4b .

The invention relates to a balance wheel 1 for a clock movement. The balance comprising rigid parts constituted by a hub 2 whose center defines the pivot axis D of the balance 1, a rim 3, and at least one arm 4 connecting the rim 3 to the hub 2.

Depending on the needs of those skilled in the art, the balance wheel is made of copper, or of a copper alloy such as nickel silver. The balance wheel can also be made of aluminum, of an aluminum alloy, of titanium or titanium alloy, of gold or gold alloy, of platinum or platinum alloy.

The balancer 1 also comprises at least one elastic arm 5 comprising a first end 5B secured to the rim of the balancer 1, and a second distal end 5A free relative to the hub 2, to the arm 4, and to the serge sector 3, the free end 5A being able to deform in the plane of the serge and tighten a weight 6 on the balance. The balance also has a slot 7 capable of receiving the weight 6, the slot 7 being delimited on the one hand by the free end 5A of the elastic arm, and on the other hand by a rigid part 8 secured to the rim and the hub . The slot 7 has an opening 9 allowing the end 5A of the elastic arm to move perpendicularly relative to the arm 4 and to be in contact with the flyweight 6 to tighten it against the arm 4 when the latter is placed in the slot .

According to the invention, the elastic arm 5 comprises a body 5C in the shape of a hook, the free distal end 5A of the hook being parallel to a part of the balance which has a rigidity greater than or equal to that of the elastic arm 5, such a shape of hook allows a good distribution of stresses while limiting the bulk in the free space between the serge and the hub.

Furthermore, such a geometry makes it possible to stress the bottom of the housing formed by the elastic arm 5, namely the interior surface S1, in compression and no longer in traction as usual in the state of the art. This has the main advantage of compensating for defects that may form such as microcracks; this zone working in compression therefore becomes less subject to these defects.

As can be observed in the figure 2 , the free distal end 5A of the elastic arm 5 has a flat 50 disposed opposite the part of the balance having a rigidity greater than or equal to that of the elastic arm 5, the rigid part being able to be an arm 4 of the balance or another elastic arm 5 for example.

It will be noted that the elastic arm 5 comprises an interior surface S1 of constant curvature over an angle α, at the center of the center circle C, greater than 240°, such a configuration making it possible to make the arm work in compression along the interior surface S1.

The elastic arm 5 also includes a constant section over an angle β, at the center of the center circle C, greater than 150°, such a configuration making it possible to have more material under stress.

The flat 50 extends over an angle γ, at the center of the center circle C, between 20° and 50°.

Advantageously, the slot 7 extends parallel to a radial R coming from said pivot axis D, and opens into a housing 10 and includes a notch 11 to precisely position the flyweight 6 and hold it in place. The width of the opening 9 is provided less than the diameter of the weight or the weight rod to hold the weight in place.

The weight 6 comprises a head 61 comprising an adjustment profile 63 arranged to cooperate with a tool. The flyweight 6 may include a rod 62 which extends this head 61, which has a diameter greater than that of the rod 62.

In the example illustrated in the figures, the flyweight 6 is equipped with a foot 65, which the rod 62 then connects to the head 61, the latter and the foot 65 then both having a diameter greater than that of the rod 62, so as to limit the travel of the flyweight 6 at the level of the elastic arm 5, in a direction parallel to the pivot axis D, or even to immobilize it in this direction.

The rod 62 extends along an axis passing through the center of the weight 6, once pinched by the elastic arm 5, the weight can be angularly orientated around this axis by means of a tool on the adjustment profile 63. The flyweight 6 has an unbalance around this axis, which results for example from a flat 64 made on the head 61, as visible in Figure 2a.

When the weight 6 is placed in the notch 11 of the opening 9, the free end 5A of the elastic arm 5 is moved perpendicular to the general direction of the radius connecting the attachment of the rigid arm to the hub and to the serge relative to to the rigid wall 8. The free end 5A has a face flat, opposite the notch 11, to provide good support for the rod of the weight 6.

The flyweight 6 comprises a rod 62 whose minimum diameter is greater than the width of the slot 7 in the free state, and whose maximum diameter is less than the width of the slot 7 when the elastic arm 5 is moved away from the rigid part 8 of the balance 1 delimiting the slot 7 under the effect of a spacing force applied to the slot 7 or to the elastic arm 5.

According to the invention, the elastic arm 5 forms a housing 10 delimited by a wall 50, the body 5C of the elastic arm being arranged to deform elastically during the assembly of the flyweight 6 to the balance, the free end 5A of the arm elastic 5 being able to move substantially perpendicularly, in the plane of the serge, relative to the arm 4.

As shown on the Figure 3 , the housing 10 has a circular shape with center C, interior radius R1 and exterior radius R2, the distance between the two radii R1 and R2 representing the thickness of the arcuate portion.

Advantageously, the body 5C of the elastic arm 5 has a first portion in the shape of an arc of a circle of constant section. The arc shape makes it possible, on the one hand to increase the surface over which the stresses are distributed, and on the other hand to store a maximum possible elastic energy thanks to a larger volume of material under stress compared to to the prior art. The body 5C also comprises a second portion in the extension of the first portion, the second portion being parallel to said arm.

As can be observed in the figure 2 , the first portion of the arm has a greater thickness compared to the second portion. Such a configuration makes it possible to have more material under stress and therefore to store more energy and thus restore a good holding force on the flyweight 6. In the present case, the first arc-shaped portion of circle undergoes very little plastic deformation while providing very good support for the flyweight.

The second portion of the arm, arranged parallel to the rigid part 8, has a lesser thickness compared to the first portion. The second portion of the elastic arm can be considered as an embedded beam of non-constant section stressed in bending, the body 5C therefore undergoes very little plastic deformation.

According to the tests carried out by the inventors, the elastic arm 5 undergoes only 0.3% of plastic deformations along the wall of the arcuate portion while the solution used in the prior art undergoes 2% of plastic deformations. . The solution used therefore makes it possible to reduce the stresses experienced by the elastic arm 5 during the installation of the flyweight 6. Such geometry makes it possible to stress the interior wall of the arcuate portion of the elastic arm 5 in compression and the outer wall in tension. Such a configuration also makes it possible to limit, or even eliminate, the formation of weakened zones such as microcracks which are harmful to the proper maintenance of the weight over time.

The dimensions and geometry of the elastic arm 5 are determined to obtain a minimum desired holding force of the flyweight, the holding force obtained by the elastic arm being at least 0.7N.

Likewise, the length and width of the arcuate portion of the elastic arm 5 are determined to remain below a stress level in order to avoid plastic deformation. The dimensions of the elastic arm 5 make it possible to store a significant elastic energy resulting from the deformation of the arm, the deformation energy being restored in the form of a holding force on the rod of the flyweight clamped by the elastic arm 5, which ensures its strength and torque in notch 11.

It will also be noted that the housing 10 formed by the elastic arm 5 has a relatively large radius at the bottom of curvature, this particular shape is determined to obtain a better distribution of stresses during the assembly of the flyweight 6, the stresses being distributed over a much larger surface compared to the prior art, this makes it possible to avoid weakening of the structure along of the curvature formed by the arc of a circle. Indeed, in the prior art the radius at the bottom of curvature of the holding member is much smaller, which implies a very localized distribution of stresses, the formation of microcracks at this location, and therefore a progressive reduction in the holding strength over time.

).The invention makes it possible, through the particular geometry of the elastic arm 5, to obtain a satisfactory holding force for the flyweight and to eliminate the formation of weakened zones when the arm is moved to place the flyweight 6. It appears that the quantity of material under stress is decisive for exerting a satisfactory holding force on the flyweight (According to Clapeyron's formula, the elastic energy stored in the material body is equal to the work of all the forces applied, W = $\frac{1}{2}{\displaystyle {\sum }_i^{\mathrm{not}}\overrightarrow{\mathit{F\iota }}\Delta \overrightarrow{\mathit{d\iota }}}$

).

The ideal solution would therefore be to increase the quantity of material under stress as much as possible so that the elastic arm restores greater holding force. However, such an option implies a greater bulk for the elastic arms, which would significantly modify the inertia of the balance and complicate the assembly of the latter, in particular the bolting.

According to the embodiments, illustrated in figure 1 And Figure 3 , the balance can include two or four elastic arms 5.

1. a) placer le balancier 1 sur un support et le maintenir en place ;
2. b) déplacer l'extrémité libre 5A du bras élastique 5 perpendiculairement dans le plan de la serge, par rapport au bras 4 ;
3. c) placer la masselotte 6 au niveau de l'encoche 11 de sorte que le pied 65 coïncide avec l'emplacement de l'encoche 11, ;
4. d) déplacer la masselotte 6 selon une direction rectiligne vers l'encoche 11 pour loger le pied 65 dans cette dernière.

The invention also relates to a method of mounting a weight on a balance wheel as described above. The assembly method according to the invention comprises the following steps:

1. a) place the balance 1 on a support and hold it in place;
2. b) move the free end 5A of the elastic arm 5 perpendicularly in the plane of the serge, relative to the arm 4;
3. c) place the weight 6 at the level of the notch 11 so that the foot 65 coincides with the location of the notch 11;
4. d) move the weight 6 in a rectilinear direction towards the notch 11 to accommodate the foot 65 in the latter.

The method may include an optional step following step c) during which the flyweight 6 is finely positioned so that the head of the flyweight is in contact with the upper face of the arm 5 and the upper face of the rigid wall 8.

The invention also relates to a balance wheel 1 which comprises a plurality of holding members 5, each being arranged to receive at least one weight 6.

The invention also relates to a watch movement comprising at least one such balance 1 as described above.

The invention also relates to a timepiece comprising at least one such movement, and which is preferably a watch.

Claims (14)

1. A balance (1) for a horological movement, comprising rigid parts consisting of a hub (2) defining the pivot axis (D) of said balance (1), at least one felloe sector (3) and at least one arm (4) connecting said at least one felloe sector (3) to said hub (2), the balance (1) including at least one slot (7) for receiving and pinching in position an inertia-block (6), said at least one slot (7) opening into a housing (10) delimited on the one hand by one of said rigid parts (2, 3, 4) of said balance (1), and on the other hand by an elastic arm (5) including a first end (5B) integral with the felloe of said balance (1), and a second distal end (5A) which is free relative to said hub (2), said arm (4), and said felloe sector (3), wherein the housing (10) has a circular shape with a centre C, said elastic arm (5) comprising a body (5C) in the shape of a hook, the free distal end (5A) of the hook being parallel to one of said rigid parts (2, 3, 4) of the balance, and wherein the elastic arm (5) comprises an inner surface (S1) of constant curvature over an angle α, at the centre of the circle with a centre C, greater than 240°.
2. The balance (1) according to claim 1, characterised in that the free distal end (5A) of the elastic arm (5) has a flat surface (50), the flat surface (50) being disposed opposite one of said rigid parts (2, 3, 4) of the balance.
3. The balance (1) according to one of the preceding claims, characterised in that the elastic arm (5) comprises a constant section over an angle β, at the centre of the circle with a centre C, greater than 150°.
4. The balance (1) according to claim 2, characterised in that the flat surface (50) extends over an angle γ, at the centre of the circle with a centre C, comprised between 20° and 50°.
5. The balance (1) according to one of claims 1 to 4, characterised in that the slot (7) extends parallel to a radial (R) coming from said pivot axis (D).
6. The balance (1) according to one of claims 1 to 5, characterised in that the elastic arm (5) is shaped to remain under a plastic deformation threshold of 0.3% at the bottom of the housing (10) during a substantially vertical elevation of the elastic arm (5) relative to the arm (8) of the balance when positioning the inertia-block (6).
7. The balance (1) according to one of claims 1 to 6, characterised in that said housing (10) is of circular shape with a centre (C) and a radius (R1) with an inlet defined by the slot (7) and a back.
8. The balance (1) according to one of claims 1 to 7, characterised in that the elastic arm provides a holding force of at least 0.7N when the inertia-block (6) is mounted.
9. The balance (1) according to one of claims 1 to 8, characterised in that one of said rigid parts (2, 3, 4) comprises a notch (11) for positioning the inertia-block (6), the width of the opening being less than the diameter of the inertia-block.
10. The balance according to one of the preceding claims, characterised in that said at least one elastic arm (5) is made integrally with the balance (1).
11. The balance according to one of claims 1 to 10, characterised in that it comprises several elastic arms (5), the elastic arms being disposed in central symmetry having as centre that of the balance.
12. A horological movement including at least one balance (1) according to one of claims 1 to 11.
13. A timepiece including at least one movement according to claim 12, the timepiece being a watch.
14. A method for mounting an inertia-block (6) on a balance (1) according to claims 1 to 11, the mounting method comprising the following steps:

    a) placing the balance (1) on a support and holding it in place;

    b) placing the inertia-block (6) at the housing (10) so that a foot (65) of the inertia-block (10) rests in the housing, the foot (65) being positioned in alignment with the slot (7);

    c) moving the inertia-block (6) in a rectilinear direction towards the slot (7) to house the foot in the notch (11), the foot of the inertia-block spreading the elastic arm (5) during its movement.

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