Method for treating a beard trimmer, and method for manufacturing a beard trimmer

Abstract

To provide a method of treating a balance spring to reduce velocity drift.SOLUTION: A method of treating at least one balance spring intended to be incorporated in a horological movement is provided, the balance spring being made of a Nb-Ti alloy and the method comprising a step of steaming (called climatic steaming) in a temperature range of 30 to 100°C in an atmosphere with a relative humidity in a range of 60 to 99%.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for treating a balance spring for a watch movement. It also relates to a balance spring obtained from this treatment method.

Background Art

[0002] Watch manufacturers are well aware that the frequency of a balance spring oscillator drifts as a function of time.

[0003] To reduce this drift, it is common to perform a steam treatment consisting of heating the balance spring for between 6 hours and 24 hours at a temperature between 100 and 250 °C. The steam treatment has the effect of restoring the material and allowing the diffusion and rearrangement of interstitial elements, namely carbon, nitrogen and oxygen, and the effect of stabilizing the natural oxide layer. Despite the steam treatment, in balance springs made of Nb-Ti alloy, a rate drift exceeding 6 s / d was still observed after one year.

Summary of the Invention

[0004] An object of the present invention is to propose a new method for treating a balance spring to reduce the rate drift. The method is applied to balance springs made of paramagnetic alloys, in particular to balance springs made of Nb-Ti alloy in which the weight percentage of Ti relative to the total weight of the alloy is between 40 and 90%, preferably between 40 and 50%.

[0005] According to the present invention, the method for treating a balance spring includes a step of steam treatment called climate steaming. This is because this steam treatment is carried out in an atmosphere having a controlled level of relative humidity.

[0006] More specifically, the present invention relates to a method for treating at least one hairspring intended to be equipped with a timepiece movement. The hairspring is made of an Nb-Ti alloy, and the method includes a step of steam treatment, called climatic steaming, in an atmosphere having a relative humidity between 60 and 99% and in a temperature range between 30 and 100 °C.

[0007] According to tests, a clear decrease has been shown in the rate drift of the hairsprings treated by the method according to the present invention. This improvement may be due to the formation and growth of different forms of TiO on the surface of the hairspring due to humidity. 2 This may also be related to the presence of water molecules adsorbed on the surface of the hairspring.

[0008] The present invention also relates to a hairspring having the characteristic that its rate is 3 s / d or less after 5 months of use from the time the climatic steaming step is performed.

[0009] Other features and advantages of the present invention will become apparent from the following description and drawings.

Brief Description of the Drawings

[0010]

Figure 1

Embodiments for Carrying Out the Invention

[0011] The present invention relates to a method for treating a hairspring intended to be equipped with a balance wheel of a timepiece movement.

[0012] According to the present invention, the treatment method can be carried out on individual whisker magnets or in batch on several whisker magnets. This can be done, for example, on a plate containing several whisker magnets in a barrel. This can also be done on the entire watch movement to which the whisker magnets are attached. By way of example, this can be an assembly comprising a whisker magnet and a collet, or an assembly formed by an oscillator comprising a template, a whisker magnet, a plate and a shaft.

[0013] The whisker magnet is made of a paramagnetic alloy, in particular an Nb-Ti alloy. This alloy contains titanium in an amount between 40 and 90% by weight, with possible traces of one or more elements selected from O, H, C, Fe, Ta, N, Ni, Si, Cu, Al, each of said elements being between 0 and 1600 ppm of the total weight, and the balance of 100% being constituted by niobium.

[0014] According to the present invention, the treatment method of the whisker magnet includes a steaming step in a temperature range between 30 and 100 °C in an atmosphere having a relative humidity between 60 and 99%. Preferably, the temperature range is between 40 and 80 °C, more preferably between 40 and 60 °C. Preferably, the relative humidity is between 70 and 97%, preferably between 85 and 95%, more preferably between 87 and 95%. More preferably, the test is carried out at normal pressure. It is also possible to carry out the test at a partial pressure between 1 and 1000 mbar. For example, it is also possible to carry out an overpressure test at a pressure between 1 and 5 bar in a steamer. A fairly wide range of holding times between 10 minutes and 100 hours is possible, and the time does not have a significant influence on the result.

[0015] The climatic steaming treatment according to the present invention preferably precedes a standard steaming treatment well known in the prior art. This standard steaming treatment is carried out under ambient humidity at a temperature between 100 and 250 °C and is preferably carried out in a period between 1 and 30 hours.

[0016] The standard steaming treatment and the climate steaming treatment are carried out after the beard straightening fixing step, which is a heat treatment well-known to those skilled in the art.

[0017] Therefore, the method for manufacturing the beard straightener of the present invention includes the following steps having steps a) to f) well-known to those skilled in the art. a) Manufacture of a blank made from an Nb-Ti alloy having the above chemical composition. b) Solution quenching treatment of the blank, known as β-type, to make titanium and niobium essentially in the form of a β-phase solid solution. c) Application of a deformation sequence to the alloy having optionally one or more heat treatments. Deformation means deformation by drawing and / or rolling. Drawing may require the use of one or more dies, if necessary, during the same sequence or in different sequences. The wire is drawn until it has a round cross-section. Rolling can be carried out in the same deformation sequence as drawing or in a different sequence. Advantageously, the last sequence applied to the alloy is rolling, preferably rolling with a rectangular profile adapted to the inlet cross-section of the winding spindle. d) Winding to form a beard straightener. e) Final heat treatment for fixing. f) Optional standard steaming treatment. g) Climate steaming treatment according to the present invention.

[0018] The present invention also relates to a beard straightener obtained from the treatment method according to the present invention. The characteristic of this beard straightener is that it contains titanium oxide and potentially adsorbed water molecules on its surface. It also has the characteristic that after 5 months of use after the climate steaming step, its speed is less than 3 s / d, or even less than 2 s / d.

[0019] The test was conducted after the climate steaming step. The results are shown in Fig. 1. The vertical axis is the speed (s / d) measured by Witschi's Chronomaster device at room temperature, and the horizontal axis is the time in months. The test was carried out on a Nb-Ti alloy mustache with a Ti weight percentage of 47%. According to the method of the present invention, this mustache was subjected to the standard steaming method according to step f) performed at 150 °C for 24 hours at ambient humidity, and then to the climate steaming method according to step g) performed at a temperature of 50 °C for 4 hours in an atmosphere with a relative humidity of 93% under normal pressure. For comparison, mustaches of the same chemical composition that did not undergo the treatment according to step f) or g) were also tested. Mustaches of the same chemical composition that received only the standard steaming according to step f) performed at 150 °C for 24 hours at ambient humidity were also tested. A clear reduction in speed drift was observed in the mustaches made using the treatment method according to the present invention. After 5 months, the speed was on the order of 2 s / d compared to values on the order of 5 s / d for the comparative control mustaches.

Claims

1. 1. A method for treating at least one hairspring intended to equip a timepiece movement, comprising the steps of: the hairspring is made of a Nb-Ti alloy; The method includes a step of steam treatment, called climate steaming, in an atmosphere having a relative humidity between 60 and 99%, at a temperature range between 30° C. and 100° C.

2. 2. The method of claim 1, wherein the climate steaming step precedes a standard steaming step carried out under ambient air at a temperature range between 100 and 250°C.

3. 2. The method of claim 1, wherein the temperature range of the climate steaming step is between 40 and 80°C.

4. The method of claim 1 , wherein the relative humidity is between 70 and 97%.

5. The method of claim 1, wherein the method is carried out under normal pressure.

6. The method of claim 1, wherein the method is carried out under a partial pressure of between 1 and 1000 mbar or under an overpressure with a pressure of between 1 and 5 bar.

7. 10. The method of claim 1, wherein the method is carried out under normal pressure in an atmosphere containing a relative humidity between 87 and 95% having a temperature between 40 and 60°C.

8. 2. The method of claim 1, wherein said Nb-Ti alloy comprises a weight percentage of Ti between 40 and 90% with possible traces of one or more other elements selected from O, H, C, Fe, Ta, N, Ni, Si, Cu and Al, each of said elements being between 0 and 1600 ppm of the total weight, with the balance of 100% being constituted by Nb.

9. The method of claim 1, wherein the at least one hairspring includes multiple hairsprings in a plate or a single hairspring mounted in an assembly of the watch movement, and the treatment is applied to each of the plate or the assembly.

10. the assembly includes the balance spring and a collet; 10. The method according to claim 9, wherein the assembly is formed by an oscillator including a balance, a hairspring, a plate and an axis.

11. 2. A method for manufacturing at least one hairspring, comprising a fixing step prior to the method according to claim 1.

12. A method according to any one of claims 1 to 10, wherein the speed of the at least one hairspring after 5 months of use following the climatic steaming step is 3 s / d or less.

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