EP3743538A1

EP3743538A1 - Pivoting pin of a regulator

Info

Publication number: EP3743538A1
Application number: EP19702055.5A
Authority: EP
Inventors: Maxime Danielou
Original assignee: Richemont International SA
Current assignee: Richemont International SA
Priority date: 2018-01-26
Filing date: 2019-01-24
Publication date: 2020-12-02
Anticipated expiration: 2039-01-24
Also published as: EP3743538B1; WO2019145434A1; CH714594A1

Abstract

The invention relates to a pivoting pin of a regulator of a clockmaking mechanical movement consisting of a material comprising, in weight percentage: between 25% and 55% of palladium; between 25% and 55% of silver; between 10% and 30% of copper; between 0% and 5% of zinc; between 0% and 2% of at least one element selected from rhenium, ruthenium, gold and platinum; and between 0% and 1% of at least one element selected from boron and nickel.

Description

Pivot shaft of a regulating member

Technical area

The present invention relates to the field of watchmaking. It relates, more particularly, to a pivot axis of a regulating member of a clockwork mechanical movement and more particularly to a pendulum, anchor or escapement axis made of a non-magnetic material.

State of the art

[0002] The manufacture of clock-type pivot axes such as a rocker shaft, an anchor rod or an escape pinion consists in carrying out a succession of operations making it possible, from a bar of raw material, to form an axis having precise dimensional characteristics as well as a sufficient mechanical resistance with regard to the envisaged application.

[0003] By their general shape of revolution, the clockwise pivot axes are made in a known manner by machining operations or precision turning, from a carbon martensitic steel bar. These machining operations make it possible to define the functional surfaces necessary for the proper functioning of the axis (clearances, stops, pivots, etc.) and the assembly of the various components (balance seat, bearing surface, bearing surface of the ferrule , etc.). The neckline then undergoes a deburring operation and then one or more heat treatment operations comprising at least one quenching to improve the hardness of the axis and income to improve toughness. A rolling operation of the pivots, intended to improve the surface state, the hardness and the geometric precision, is generally carried out during or at the end of manufacturing. The rolling operation can be compared to an operation of grinding and / or polishing the pivots.

More specifically, the pivot axes, for example the balance axes, used in a traditional manner in the mechanical clockwork movements are made from carbon martensitic steel bars having addition elements of the type lead and / or manganese. Manganese is generally present in steels in the form of manganese sulphides and allows a regular fragmentation of the cutting chip. Lead tends to bind to non-metallic inclusions present in steel, or is in the form of elementary particles. It acts as a lubricant, reduces the coefficient of friction at the tool / cutting area interface and limits the formation of a material deposit on the cutting edge of the tool. These addition elements therefore have the common objective of improving the machinability of the steel. A steel of this type can be supplied from a large number of suppliers under the name 20AP or 1.1268 + Pb.

In addition to good machinability, the lead martensitic steel has, after quenching and tempering treatments, high mechanical properties in adequacy with the stresses encountered by the pivot axes during their operation. Typically, the pivots of an axis made of lead martensitic steel have a hardness exceeding 600 HV1 after heat treatment and rolling. Such hardness values guarantee an optimum wear resistance for the oscillator's proper operation over time.

Despite the advantages of machinability and strength, lead martensitic steel has a major disadvantage: its sensitivity to magnetism. The environment in which watches operate, has has evolved considerably in recent decades. Electronic devices and accessories incorporating permanent magnets have multiplied, exposing the watches, and thus the regulating organs of the latter, magnetic fields increasingly high and more and more frequent. The lead martensitic steel commonly used for the production of balance shafts has a non-negligible residual field after exposure to an external magnetic field. The proximity of the axis with the spiral, generally made of ferromagnetic material, makes it a particularly strategic component when it is desired to improve the magnetism resistance of watches.

It will be noted that carbon martensitic steels are also susceptible to corrosion. This disadvantage is a problem mainly during the steps of manufacturing and storing axes. In use, the pivot axes of the mechanical movement normally remain confined within the sealed zone of the watch, which does not represent a particularly constraining medium for a material, even oxidizable.

The document CH707503 describes a pivot axis formed of a composite material having a metal matrix comprising at least one metal selected from nickel, titanium, chromium, zirconium, silver, gold, platinum , silicon, molybdenum, aluminum or an alloy thereof, said matrix being charged with hard particles selected from WC, TiC, TaC, TiN, TiCN, Al 2 O 3, ZrO 2, O 2 O 3, SiC, MoSi 2, AlN or a combination of these, in order to limit the sensitivity of the axis to the magnetic fields. The hardness of said composite material is greater than or equal to 1000 HV1. The solution described here is not optimal. Cutting tool machining of metal matrices loaded with hard particles generates premature tool wear. In operation, the pivoting of such an axis in a ruby bearing also generates premature wear at the bearing.

[0009] Document CH707504 describes a titanium or titanium alloy pivot pin in order to limit its sensitivity to magnetic fields. At least the outer surface of the pivots is partially or fully hardened relative to the axis core to a predetermined depth, the outer surface has a hardness greater than 800 HV1. The solution described here is not optimal. The superficial hardening of the pivots adds a step in the already complex process of obtaining a pendulum axis. In addition, titanium alloys require special precautions during machining, particularly with regard to the risk of fire.

The document CH707505 describes a steel pivot axis of the austenitic type, a cobalt alloy of the austenitic type or a nickel alloy of the austenitic type to limit its sensitivity to magnetic fields. At least the outer surface of the pivots is hardened relative to the heart of the axis to a predetermined depth, the outer surface has a hardness greater than 1000 HV1. The solution described here does not seem optimal. The superficial hardening of the pivots adds a step in the already complex process of obtaining a pendulum axis. This hardening occurring after the step or ends of the pivots, the handling precautions taken during this processing step must be important to avoid the risk of marking or bending the pivots.

EP3273303 discloses a balance shaft made of a non-magnetic alloy of copper. During the manufacture of the axis, the pivots are rolled or polished in order to remove an extra thickness of material and thus to reach the final dimensions and surface condition. On the other hand, the surface is hardened by means of a heat treatment and / or thermochemical diffusion or ion implantation of other atoms, to a predetermined depth. This alloy, after treatment, may have an interesting hardness, greater than 600 HV, but the treatment processes used are complicated, require specialized equipment and are difficult to control, particularly with regard to ion diffusion. EP3273304 also discloses an axis made of a similar alloy, which is provided with a layer of hard material deposited on its surface. Ideally, it is intended to avoid an additional deposit of surface, which is again complicated to perform and requires specialized equipment.

US9194024 discloses an alloy for jewelry, whose composition is chosen to obtain a substantially white color, comparable to platinum alloys. After curing by aging, the alloy reaches a hardness up to about 240 HV, which is insufficient for a watch axis.

The object of the present invention is to provide an axis made of a nonmagnetic material as an alternative to the various solutions of the prior art and remedying, at least partially, their disadvantages.

Disclosure of the invention

More specifically, the invention relates to a pivot axis of a regulating member of a clockwork mechanical movement made of an alloy comprising or consisting of weight:

between 25% and 55% of palladium;

- between 25% and 55% silver;

between 10% and 30% copper;

between 0% and 5% of Zinc;

between 0% and 2% of one or more elements selected from rhenium, ruthenium, gold and platinum;

between 0% and 1% of one or more elements chosen from boron and nickel. Preferably, the invention relates to an alloy of the type consisting of 41% of palladium, 37.5% of silver, 20% of copper, 1% of zinc and 0.5% of platinum.

The invention also relates to a method of manufacturing a pivot axis of a regulating member of a mechanical clockwork movement comprising the following steps:

- To obtain an alloy bar comprising between 25% and 55% of Palladium, between 25% and 55% of Silver, between 10% and 30% of Copper, between 0% and 5% of zinc, between 0% and 2% % of one or more elements selected from rhenium, ruthenium, gold and platinum, and between 0% and 1% of one or more elements selected from boron and nickel;

- Uncut the axis with an allowance relative to a predetermined dimension;

- Carry out a treatment operation of the surface state of the axis with removal of the extra thickness to reach the predetermined dimension.

The manufacturing method may further comprise a curing heat treatment step between the machining and surface treatment steps.

Brief description of the drawings

Other details of the invention will appear more clearly on reading the description which follows, given with reference to the accompanying drawing in which:

- Fig. 1 is a representation of a pivot axis according to the invention, in the cleavage stage;

- Fig. 2 is a representation of a pivot axis according to the invention, the rolled stage;

- Fig. 3 is a representation of a pivot axis according to the invention, in the finished stage; - Fig. 4 is a representation of a pivot axis according to the invention, showing the different thicknesses that may be involved in the process.

Embodiment of the invention

The invention relates to a pivot axis of a regulating member of a mechanical clockwork movement, and more particularly to a balance beam axis, anchor or escape mobile.

The Applicant has identified an alloy family having properties of particular interest for application to axes of mechanical movement regulating member, especially in terms of magnetism and oxidation resistance.

The alloys of this family have, by weight:

- between 25% and 55% palladium

- between 25% and 55% of silver

- between 10% and 30% copper

between 0% and 5% of zinc

between 0% and 2% of one or more elements selected from rhenium, ruthenium, gold and platinum

between 0% and 1% of one or more elements chosen from boron and nickel.

[0022] Preferably, the alloys in question comprise by weight:

- between 38% and 43% of palladium; and or

- between 35% and 40% of money; and or

- between 18% and 23% copper; and or

- between 0.5% and 1.5% zinc.

More particularly from this family of alloys, an alloy of the type consisting of 41% of palladium, 37.5% of silver, 20% of copper, 1% of zinc and 0.5% of platinum does not present an attractive action. detectable when exposed to a permanent magnet. Neither does it exhibit measurable remanent magnetization after exposure to the magnet.

The Applicant has also identified that Palladium-Silver-Copper alloys exhibit a higher oxidation resistance than that of carbon martensitic steels thanks in particular to the presence of palladium, a chemical element of the platinum group. Palladium makes it possible to improve the following characteristics of the alloy, which are particularly interesting in the case of use for a pivot axis: chemical inertness, resistance to corrosion and oxidation, low coefficient of thermal expansion and mechanical durability.

Another aspect of the invention relates to a method of manufacturing a pivot axis of a regulating member which we will now describe the steps.

The first step in the process of obtaining an axis according to the invention is to provide a free-cutting bar of the alloy Palladium-Silver-Copper having a composition belonging to the family of alloy such as defined above. Different shades are available from various suppliers. The latter perform the steps of alloying and the steps of shaping the bar (drawing, drawing ...) to provide a bar in the standard dimensions of bar turning. Generally 2-3mm in diameter over 2000-3000mm long. It goes without saying that the chemical composition of the bar will be similar to that of the axis made from this bar.

The Vickers hardness of the stretched material for producing the axis according to the invention is of the order of 260-310 HV1. After thermal hardening at 380-420 ° C, the hardness value rises to 460-500HV1. This heat treatment can last between 30 minutes and 2 hours, more particularly between 45 minutes and 1 hour 30 minutes, even more especially for 1 hour, and hardness value after curing remains lower than can be found on a 20AP steel after rolling, typically more than 700HV1.

The curing heat treatment can be performed at any time of the process of obtaining the axis. This hardening can be carried out on the receiving bar if the machining requires a high hardness. Preferably, the hardening is performed after machining and before the step or steps of treatment of the surface state of the axis.

When the Hertz pressure is quantified at the pivoting point of the axis, it can be seen that the low Young's modulus of the Palladium-Silver-Copper alloy makes it possible to lower the maximum pressure observed at the level of the axis. contact of the axis with the pivot stone. During a contact between two Young modulus materials Ei and E2, the equivalent modulus of elasticity E used to determine the stiffness of the contact is calculated as follows:

The maximum pressure observed at the contact is given by the following formula:

Pmax- 0.418

F = normal force on the contact

E = modulus of elasticity previously defined

rr and I = are geometrical parameters of the contact.

For a given normal force F, and with equivalent contact geometry, we observe that the maximum pressure is proportional to Ë. With a digital application, we find that Ë is down more than 20% when we go from a contact steel (220GPa) on ruby (350GPa) to a contact PdAgCu alloy (100GPa) on ruby (350GPa) with equivalent geometry.

Thus, despite a lower hardness, it is found that the wear resistance of the contact is still satisfactory. This is explained by the lowering of the contact pressure, thus making it possible to use an axis with a lower hardness without compromising the resistance to wear of the contact, typically 460-500HV1 for the axis made of Palladium-Silver alloy -Cuivre against 600-700HV1 for a standard axis in Carbon Martensitic Steel. The use of an alloy of lower hardness facilitates material removal and shaping operations.

The next step in the process of obtaining an axis according to the invention is to shape it by a bar turning step. This is performed in a traditional manner on the same equipment as those used to machine martensitic carbon steel axes according to the prior art. An adaptation of the cutting parameters is necessary in order to optimize the quality and the efficiency of the machining step. In the case of the axis of the balance, its radius being very small, even at high spindle speed, the cutting speeds achieved during machining are limited. Referring to FIG. 1, the balance shaft has two zones of small diameter, the pivots 10 located at the ends of the axis as well as several zones of greater diameter forming the body of the axis 20.

For example, at the pivots, it is possible to use a cutting speed of 20 to 23 m / min with an advance of 0.0015 mm / rev. At the axle body, a cutting speed of 20 to 23 m / min and an advance of 0.002 mm / rev to 0.005 mm / rev can be used.

During this bar turning step, it is necessary to provide one or more thicknesses depending on the processing operations of the projected surface state of the axis. If the machining step is sufficiently repeatable and provides a geometric tolerance sufficient for the intended application, a simple polishing of the functional areas should be performed. An extra thickness (e1) corresponding to the amount of material removed during polishing should be added to the part in relation to the final dimensions. FIG. 2 illustrates, by way of example, a balance shaft after the bar turning step. Figure 3 illustrates, by way of example, a balance shaft after the polishing step. Referring to FIG. 4, the bar turning step will make it possible to obtain the profile 2 at the pivot with an excess thickness (e1) with respect to the profile 1. The polishing step will bring the profile of the pivot to its level. final profile 1. The extra thickness (e1) is typically of the order of 2pm to the diameter but can be adapted according to the polishing envisaged (duration, type of abrasive particles used ...).

According to another variant of the method, if we consider a step of grinding or rolling pins for fine control of the dimensions and surface conditions, an excess thickness (e2) corresponding to the amount of material removed during this step grinding or rolling must be added to the workpiece or to the pivots at the bar turning stage. The extra thickness (e2) is typically of the order of 20 μm over the length and 5 μm over the diameter but can be adapted in rolling or grinding function envisaged. The turning must therefore be at the level of the profile 3, as shown in Figure 4. The rolling will bring the pivot at the level of the profile 2 as shown in Figure 4. A treatment of the surface condition may be added at the end of the process to get Profile 1.

Depending on the type of treatment of the selected surface state, loose or localized at the pivots, the skilled person will consider an extra thickness on the entire axis if the treatment is carried out in bulk or only areas affected by the removal of material if it is a spot treatment.

Other steps of treatment of the surface state of the axis or pivots with removal of material can be envisaged without departing from the scope of the invention: electrolytic polishing or laser polishing for example. The skilled person will adapt the extra thickness to be taken into account in the bar turning step.

Intermediate stages of washing and dimensional control can be integrated into the process.

Other types of parts incorporated in a mechanical watch movement or quartz, and likely to disrupt the operation of the movement in case of magnetization, can be made in an alloy of the type described above without being part of the perimeter claimed protection. This type of part can be in particular of the pin type, screws, axes of the gears of finishing etc. without presenting problems similar to those encountered for the pivot axis of a regulating member.

Claims

claims

1. Pivoting axis of a mechanical watch movement regulating member made of a material comprising by weight:

between 25% and 55% palladium

between 25% and 55% of silver

between 10% and 30% copper

between 0% and 5% zinc

between 0% and 1% of one or more elements selected from boron and nickel.

2. adjusting member shaft according to claim 1, characterized in that said material comprises by weight between 38% and 43% of palladium.

3. axis of regulating member according to one of the preceding claims, characterized in that said material comprises by weight between 35% and 40% of silver.

4. axis of regulating member according to one of the preceding claims, characterized in that said material comprises by weight between 18% and 23% of copper.

5. axis of regulating member according to one of the preceding claims, characterized in that said material comprises by weight between 0.5% and 1.5% zinc

6. axis of regulating member according to one of the preceding claims, characterized in that said axis is a balance shaft, an anchor axis or an exhaust axis mobile.

7. adjusting member shaft according to one of the preceding claims, characterized in that it has a Vickers hardness of 460 HV1 to 500 HV1.

8. Mechanical movement for a timepiece, characterized in that it comprises a regulating member shaft according to one of the preceding claims.

9. A method of manufacturing a pivot axis of a regulating member comprising the following steps:

Obtain an alloy bar comprising between 25% and 55% of Palladium, between 25% and 55% of Silver, between 10% and 30% of Copper, between 0% and 5% of zinc, between 0% and 2% one or more elements selected from rhenium, ruthenium, gold and platinum, and between 0% and 1% of one or more elements selected from boron and nickel;

Decollete the axis with an allowance relative to a predetermined dimension;

Carry out a treatment operation of the surface state of the axis with removal of the excess thickness to reach the predetermined dimension.

10. The manufacturing method according to the preceding claim, wherein said bar has a Vickers hardness of between 260 HV1 and 310 HV1.

11. The manufacturing method according to one of claims 9 and 10, characterized in that it further comprises a curing heat treatment step.

12. The manufacturing method according to the preceding claim, characterized in that the curing heat treatment step comprises a heat treatment at a temperature of 380 ° C to 420 ° C.

13. Manufacturing process according to the preceding claim, wherein said curing heat treatment stage lasts between 30 minutes and 2 hours, more particularly for between 45 minutes and 1 hour 30 minutes, more particularly for 1 hour.

14. The manufacturing method according to one of claims 11 to 13, wherein, after said curing heat treatment step, said axis has a Vickers hardness of between 460 HV1 and 500 HV1.

15. The manufacturing method according to one of claims 11 to 14, characterized in that said curing heat treatment step is performed between the steps of obtaining said bar of alloy and bar turning or between the turning steps and surface treatment.

16. A method of manufacturing a pivot axis of a regulating member comprising a body provided at its ends with pivots, said method comprising the following steps:

Detaching the body of the axis with a first excess thickness relative to a predetermined first dimension, and the axis pivots with a second allowance with respect to a second predetermined dimension, said second excess being greater than the first excess thickness;

Carrying the pivots to bring them to the first oversize relative to the second predetermined dimension;

Performing a treatment operation of the surface state of the body and pivots with removal of the first thickness to reach respectively the first and second predetermined dimensions.

17. The manufacturing method according to the preceding claim, wherein said bar has a Vickers hardness of between 260 HV1 and 310 HV1.

18. The manufacturing method according to one of claims 16 and 17, characterized in that it further comprises a curing heat treatment step.

19. The manufacturing method according to the preceding claim, characterized in that the curing heat treatment step comprises a heat treatment at a temperature of 380 ° C to 420 ° C.

20. The manufacturing method according to the preceding claim, wherein said hardening heat treatment step lasts between 30 minutes and 2 hours, more particularly for between 45 minutes and 1 hour 30 minutes, more particularly for 1 hour.

21. The manufacturing method according to one of claims 18 to 20, wherein, after said hardening heat treatment step, said axis has a Vickers hardness of between 460 HV1 and 500 HV1.

22. Manufacturing process according to one of claims 18-21, characterized in that said curing heat treatment step is performed between the steps of obtaining said alloy bar and bar turning or between the turning steps and surface treatment.