Gold-based clock axis

Abstract

The present invention relates to a watch axis made of non-magnetic gold alloy, said alloy having a hardness greater than 500 HV and comprising more than 500‰ by mass of gold.

Description

[0001] The present invention relates to a gold-based watch axis, in particular a balance wheel axis, an escape wheel axis or a seconds hand axis. PRIOR STATE OF TECHNOLOGY

[0002] Mechanical watches include a resonator comprising a balance wheel and a balance spring which are usually mounted on the same shaft designated "balance axis" ( figure 1 ).

[0003] Optimizing the performance of the mechanism (precision, durability, etc.) depends heavily on the balance wheel and the quality of its pivoting.

[0004] In general, a watch axis, in particular a balance staff, must therefore meet certain constraints, notably in terms of machinability or resistance (i) to corrosion, (ii) to shocks, (iii) to breakage and (iv) to wear.

[0005] Thus, many materials have been used to manufacture watch axes, for example metal alloys such as martensitic steel, or ceramics such as yttrium oxide stabilized zirconia... Balance shafts covered with a layer of specific material have also been developed.

[0006] In any case, there remains a need for alternative materials that meet established requirements, are easy to machine, and, ideally, are non-magnetic. Indeed, martensitic steel offers adequate strength properties but remains susceptible to magnetism and corrosion (which is particularly problematic during manufacturing and storage), while ceramics remain brittle under repeated impacts. Furthermore, some materials require numerous heat and mechanical treatments to achieve the necessary strength properties.

[0007] On the other hand, the increasing presence of electronic devices constantly exposes watches to magnetic fields, which can lead to malfunctions when the watch movements are made of steel.

[0008] Therefore, there is still a need to develop alternatives that simultaneously solve all the technical problems, namely machinability and resistance to corrosion, shock, breakage and wear, and behavior in the presence of magnetic fields, or after exposure to a magnetic field.

[0009] The present invention addresses these problems through the use of a non-magnetic, high-hardness gold alloy. DESCRIPTION OF THE INVENTION

[0010] A first aspect of the invention relates to a watch axis made of a non-magnetic gold alloy, said alloy comprising more than 500‰ by mass of gold and having a hardness greater than 500 HV.

[0011] In other words, the non-magnetic gold alloy does not simply constitute a surface layer or solely the core of the watch axis.

[0012] This watch axis is not composed exclusively of stoichiometric intermetallics. On the other hand, it does not include composite material consisting of a metallic matrix and particles of oxides, carbides or nitrides (in particular WC, TiC, TaC, TiN, TiCN, Al 2 O 3, ZrO 2, Cr 2 O 3, SiC, MoSi 2 and AlN).

[0013] The clockwork axis is advantageously a balance wheel axis.

[0014] Advantageously, the watch axis has a length of less than 5 mm, preferably less than 4 mm, and even more preferably less than 3 mm. The watch axis has a length advantageously greater than 1 mm, and preferably greater than 2 mm. Advantageously, the watch axis comprises two pivots having a diameter advantageously between 0.02 mm and 0.30 mm, preferably between 0.03 mm and 0.20 mm, and even more preferably between 0.04 mm and 0.10 mm.

[0015] A balance staff allows, in particular, the support of the balance wheel rim and the balance spring of a watch movement.

[0016] A second aspect of the invention relates to a watch oscillator, comprising a balance staff according to the first aspect and at least one additional component such as a balance wheel or an elastic return element. This at least one additional component is advantageously non-magnetic, for example, an elastic return element made of a non-magnetic material. The elastic return element can thus be in the form of a balance spring made of a non-magnetic material, such as a silicon balance spring or a balance spring made of a non-magnetic metal alloy (based on NbZr, NbTi, FeMn, etc.) with its ferrule, also advantageously made of a non-magnetic metal alloy. Even more advantageously, the watch oscillator consists entirely of non-magnetic parts. For example, it can consist of a brass balance wheel, a brass or nickel silver (copper, nickel, and zinc alloy) balance plate, a corundum ellipse, and a silicon balance spring.Furthermore, a person skilled in the art may choose to combine the oscillator with an axis according to the invention with a non-magnetic escapement. For example, the anchor and / or the escape wheel may be made of non-magnetic NiP alloy or silicon.

[0017] As an example, the clock oscillator can be tested within a clock movement according to the following sequence: walking test in the 6 usual positions, exposure to an artificial magnetic field of 500 gauss, 1000 gauss or 5000 gauss for a predetermined time, walking test in the 6 usual positions, with a deviation of 20s / day maximum, advantageously 10s / day maximum, compared to the tests before exposure to magnetic fields, measurement of the stopping value under magnetic field, with a minimum of 100 gauss, preferably a minimum of 500 gauss, preferably a minimum of 1000 gauss.

[0018] The non-magnetic gold alloy used in the watch's axis contains more than 500‰ gold by mass, relative to the mass of the alloy. It has a hardness exceeding 500 HV.

[0019] Advantageously, it is an 18-karat gold alloy (750‰ by mass of gold). Preferably, the gold alloy comprises between 750‰ and 950‰ by mass of gold. Unless otherwise indicated, percentages are expressed by mass relative to the mass of the alloy (i.e., the watch axis).

[0020] Advantageously, the non-magnetic gold alloy comprises (more advantageously, the non-magnetic gold alloy consists of): at least 750‰ of gold, a first alloying element chosen from the group consisting of: 30 to 220‰ of niobium, 10 to 180‰ of vanadium, and mixtures thereof, a second alloying element chosen from the group consisting of: 30 to 70‰ of iron, 10 to 120‰ of palladium (advantageously 20 to 120‰), 10 to 120‰ of chromium (advantageously 30 to 120‰), 5 to 40‰ of titanium, and mixtures thereof, 0 to 50‰ of a third alloying element chosen from the group consisting of: nickel, manganese, copper, silver, and mixtures thereof, the total quantity of the first, second and third elements of the gold alloy being between 150‰ and 250‰.

[0021] During the preparation of the non-magnetic gold alloy, a grain refiner can be incorporated. This grain refiner advantageously represents 0 to 2000 ppm, by mass relative to the total mass of gold and the first, second, and third alloying elements.

[0022] Thus, advantageously, the non-magnetic gold alloy consists of "gold, a first alloying element, a second alloying element, optionally a third alloying element", and includes 0 to 2000 ppm of a grain-refining element.

[0023] The grain-refining element is advantageously chosen from the group consisting of: iridium, boron, vanadium, when the first alloying element is niobium, iron, when the second alloying element is chosen from the group consisting of: palladium, chromium, titanium, and one of their mixtures, cobalt, barium, yttrium, zirconium, titanium, when the second alloying element is chosen from the group consisting of: iron, palladium, chromium, and one of their mixtures, and their mixtures.

[0024] According to a first example, the non-magnetic gold alloy comprises: at least 750‰ of gold, 30 to 220‰ of niobium, 30‰ to 70‰ of chromium.

[0025] According to a second example, the non-magnetic gold alloy comprises: at least 750‰ of gold, 120‰ to 180‰ of vanadium, 30‰ to 70‰ of iron, 20‰ to 60‰ of palladium.

[0026] According to a third example, the non-magnetic gold alloy comprises: at least 750‰ of gold, 80‰ to 120‰ of palladium, 80‰ to 120‰ of chromium, 10‰ to 50‰ of vanadium, 5‰ to 40‰ of titanium.

[0027] Preferably, the non-magnetic gold alloy is chosen from (by mass): Au 650-670 Ti 330-350, Au 744-764 Nb 187-207 Cr 39-59, Au 750 Ag 100 Cr 100 Fe 50, Au 750 Nb 200 Cr 50, Au 750 V 160 Fe 50 Pd 40, Au 750 V 140 Pd 60 Fe 50, Au 750 Pd 100 Cr 100 V 30 Ti 20, Au 750 V 150 Fe 50 Nb 50, and Au 800 Nb 160 Cr 40.

[0028] The non-magnetic gold alloy is advantageously chosen from the group consisting of: Au 660 Ti 340, Au 754 Nb 197 Cr 49, and Au 800 Nb 160 Cr 40.

[0029] The hardness of the non-magnetic gold alloy is greater than 500 HV, advantageously greater than 600 HV, more advantageously greater than 700 HV.

[0030] According to a particular embodiment, the non-magnetic gold alloy may include precipitates of non-magnetic gold alloy, for example AuTi 3 precipitates when the alloy includes titanium (second alloying element) or intermetallic precipitates.

[0031] The present invention also relates to a method of manufacturing the watch axis, from the non-magnetic gold alloy as described above and below.

[0032] This process includes the following steps: preparation of a bar by mixing and heating the metals constituting a non-magnetic gold alloy having a hardness greater than 500 HV and comprising more than 500‰ by mass of gold, machining by removing material from the non-magnetic gold alloy bar in order to form a watch axis, the machining being advantageously carried out according to a technique chosen from the group consisting of: machining with cutting tools, laser, grinding and electro-erosion.

[0033] Advantageously, the process includes a hardening step carried out by work hardening (advantageously by drawing and / or hammering) and / or by heat treatment. Advantageously, before the machining step, the bar undergoes work hardening of 30% to 90%, more advantageously of 50% to 80%. Work hardening is advantageously carried out at ambient temperature, for example, at a temperature between 18 and 25°C.

[0034] Advantageously, the process includes at least one heat treatment.

[0035] Advantageously, the heat treatment is carried out at a temperature of 200 to 1100°C, more advantageously from 250 to 1000°C, and even more advantageously from 600 to 850°C.

[0036] Advantageously, the heat treatment is carried out for a period of 5 minutes to 40 hours, more advantageously from 10 minutes to 240 minutes, even more advantageously from 30 minutes to 240 minutes.

[0037] Work hardening and heat treatment can be repeated. In other words, the process can include several work hardening and / or several heat treatments.

[0038] Advantageously, the process comprises one of the following sequences: [a] first heat treatment / work hardening / machining / second heat treatment, the first (advantageously from 200 to 1100°C, more advantageously from 650 to 1100°C) and second (advantageously from 200 to 1100°C, more advantageously from 200 to 900°C) heat treatments being identical or different, [b] first heat treatment / work hardening / second heat treatment / machining, the first (advantageously from 200 to 1100°C, more advantageously from 650 to 1100°C) and second (advantageously from 200 to 1100°C, more advantageously from 200 to 900°C) heat treatments being identical or different, [c] work hardening / heat treatment / machining.

[0039] Machining is advantageously carried out using a technique chosen from the group consisting of: cutting tool machining, laser, grinding and electro-erosion.

[0040] The sequences [a], [b] and [c] above are particularly suitable for any type of machining, while sequence [c] is particularly suitable for laser machining.

[0041] Machining is advantageously carried out according to the general knowledge of the person skilled in the art, who may in particular consult document CH715613 for laser machining.

[0042] Electrical discharge machining is possible because the non-magnetic gold alloy has an electrical conductivity greater than 1 Sm-1, advantageously greater than 100 Sm-1.

[0043] Electrical discharge machining (EDM) can be carried out using a machine comprising a rotating gripping device and a wire EDM machining system mounted on a numerically controlled actuator, according to the following steps: a. to provide a bar of non-magnetic gold alloy extending along a longitudinal axis, b. to arrange the bar along its longitudinal axis on the rotating gripping member, c. to shape the bar by wire electro-erosion machining to obtain a watch axis comprising a pivot at each end, step c. comprising the continuous rotation of the bar around its longitudinal axis for the shaping of said pivots, d. optionally, tribological finishing.

[0044] Step c of electrical discharge machining may include the following steps: shaping one end of the shaft while the shaft is held by the machine on the side of a second end of the shaft, the machine taking hold of the shaft on the side of the first end previously shaped, and shaping the second end while the shaft is held by the machine on the side of its first end.

[0045] Step c. of electro-erosion machining may include one or more wire electro-erosion machining steps, by incremental rotation of the bar, to produce one or more flats or a polygonal shape.

[0046] Advantageously, the watch axis can be used for an amagnetic oscillator, in combination with other amagnetic components.

[0047] These non-magnetic components include, in particular, a spiral spring made of silicon, diamond, silicon oxide or similar; a non-magnetic metallic spiral spring; a plate made of brass or other non-magnetic material; a balance wheel made of brass or other non-magnetic material.

[0048] The present invention also relates to a watch oscillator comprising the watch axis and a non-magnetic spiral spring (preferably made of silicon or non-magnetic metallic alloy for example FeMn, NbZr or NbTi). FIGURES

[0049] There figure 1represents a clockwork axis, more precisely a balance wheel axis.

[0050] This is a representation of a conventional balance staff comprising pivots (1), a pivot (2), a stem (3) and a base (4) on which the balance wheel rim and balance spring are supported. The base (4) is also called the plate. EXAMPLES

[0051] Several watch axes were prepared from the gold alloys in Table 1, according to the following steps: preparation of a bar by mixing and heating the metals constituting the non-magnetic gold alloy, optionally, hardening by work hardening and heat treatment, machining with a cutting tool of the non-magnetic gold alloy bar in order to form a watch axis. Table 1: Hardness of gold alloys used to prepare watch axles. Example Gold alloy Hardening Hardness (Hv) INV-1 At 660 Ti 340 None - as cast 700 INV-2 Au 754 Nb 197 Cr 49 Work hardening 60% 680 Heat treatment for 20 hours at 650°C INV-3 Au 754 Nb 197 Cr 49 Work hardening 80% 730 Heat treatment 10 hours 650°C INV-4 Au 754 Nb 197 Cr 49 Work hardening 60% 650 Heat treatment for 3 hours at 700°C INV-5 Au 754 Nb 197 Cr 49 Work hardening 80% 680 Heat treatment for 1 hour at 700°C

[0052] Depending on the properties of the alloy in its as-cast state, post-treatment (work hardening and / or heat treatment) can be carried out on the alloy.

Claims

1. Watch axis made of a non-magnetic gold alloy, said alloy having a hardness greater than 500 HV and comprising more than 500‰ by mass of gold.

2. Clockwork axis according to claim 1, characterized in that The non-magnetic gold alloy contains between 750‰ and 950‰ by mass of gold.

3. Clockwork axis according to one of the preceding claims, characterized in thatThe non-magnetic gold alloy comprises, by mass: - at least 750‰ of gold, - a first alloying element chosen from the group consisting of: 30 to 220‰ of niobium, 10 to 180‰ of vanadium, and mixtures thereof, - a second alloying element chosen from the group consisting of: 10 to 70‰ of iron, 10 to 120‰ of palladium, 10 to 120‰ of chromium, 5 to 40‰ of titanium, and mixtures thereof, - 0 to 50‰ of a third alloying element chosen from the group consisting of: nickel, manganese, copper, silver and mixtures thereof, the total quantity of the first, second and third elements of the gold alloy being between 150‰ and 250‰.

4. Clockwork axis according to one of the preceding claims, characterized in that The non-magnetic gold alloy comprises: - at least 750‰ of gold, - 30 to 220‰ of niobium, - 30‰ to 70‰ of chromium.

5. Clockwork axis according to any one of claims 1 to 3, characterized in thatThe non-magnetic gold alloy comprises: - at least 750‰ of gold, - 120‰ to 180‰ of vanadium, - 30‰ to 70‰ of iron, - 20‰ to 60‰ of palladium.

6. Clockwork axis according to any one of claims 1 to 3, characterized in that The non-magnetic gold alloy comprises: - at least 750‰ of gold, - 80‰ to 120‰ of palladium, - 80‰ to 120‰ of chromium, - 10‰ to 50‰ of vanadium, - 5‰ to 40‰ of titanium.

7. Clockwork axis according to any one of claims 1 to 3, characterized in that The non-magnetic gold alloy is chosen from the group consisting of: Au 650-670 Ti 330-350 , At 744-764 Number 187-207 Cr 39-59 , At 750 Ag 100 Cr 100 Fe 50 , At 750 Number 200 Cr 50 , At 750 V 160 Fe 50 Pd 40 , At 750 V 140 Pd 60 Fe 50 , At 750 Pd 100 Cr 100 V 30 Ti 20 , At 750 Vi 50 Fe 50 Number 50 and Au 800Number 160 Cr 40 .

8. Clockwork axis according to any one of claims 1 to 3, characterized in that The non-magnetic gold alloy is chosen from the group consisting of: Au 660 Ti 340 , At 754 Number 197 Cr 49 and Au 800 Number 160 Cr 40 .

9. Clockwork axis according to one of the preceding claims, characterized in that The non-magnetic gold alloy has a hardness greater than 600 HV, advantageously greater than 700 HV.

10. Method for manufacturing the watch axle according to any one of claims 1 to 9, comprising the following steps: - preparation of a bar by mixing and heating the metals constituting a non-magnetic gold alloy having a hardness greater than 500 HV and comprising more than 500‰ by mass of gold, - machining by material removal of the bar in non-magnetic gold alloy in order to form a watch axle.

11. Method for manufacturing the watch axis according to claim 10, characterized in that Machining is carried out using a technique chosen from the group consisting of: cutting tool machining, laser, grinding and electro-erosion.

12. Method for manufacturing the watch axis according to any one of claims 10 to 11, characterized in that the process includes a hardening step by work hardening and / or heat treatment.

13. Method for manufacturing the watch axis according to any one of claims 10 to 12, characterized in that The process includes a heat treatment at a temperature of 200 to 1100°C, advantageously from 250 to 1000°C, for a period of 10 to 240 minutes.

14. Method for manufacturing the watch axis according to any one of claims 10 to 13, characterized in thatthe process comprises one of the following sequences: [a] first heat treatment / work hardening / machining / second heat treatment, the first and second heat treatments being identical or different, [b] first heat treatment / work hardening / second heat treatment / machining, the first and second heat treatments being identical or different, [c] work hardening / heat treatment / machining.

15. Clock oscillator comprising the clock axis according to any one of claims 1 to 9, and a non-magnetic spiral spring, for example a silicon spiral spring.

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