CH716862A2 - Watch movement resistant to magnetic disturbances and timepiece incorporating it. - Google Patents

Abstract

The invention relates to a mechanical watch movement, comprising, arranged in kinematic connection with each other, a source of mechanical energy, a gear train, an escapement mechanism (2) and a regulating member (1) of the balance type. hairspring, each comprising at least one mobile (10, 20, 30) pivotally mounted on a plate and / or bridge, each mobile (10, 20, 30) comprising a pivot (12, 13; 22; 32, 33) of metal at least one of its ends, characterized in that each pivot (12, 13) of the balance (10) of the regulating member (1) consists of a metal alloy, in particular of copper or of Phynox, non-magnetic or paramagnetic in order to limit its sensitivity to magnetic fields, and in that the balance spring of the regulating member (1) is also made of a non-magnetic or paramagnetic metal alloy in order to limit its sensitivity to magnetic fields.

Description

Technical area

The present invention relates to the field of mechanical watchmaking. It relates more particularly to a mechanical timepiece movement endowed with improved performance of resistance to magnetic disturbances thanks to the use of a pivot of a regulating member of the balance-spring type made of non-magnetic or paramagnetic metal alloy associated with a balance-spring also. in non-magnetic or paramagnetic metal alloy.

[0002] The invention also relates to a timepiece comprising such a mechanical movement.

State of the art

The deleterious effects of magnetic disturbances on the performance of a mechanical movement have been known for a very long time in the field of watchmaking. Indeed, any magnetic field of a few hundred Amps per meter is likely to cause the outright stopping of the movement and / or a significant and persistent disturbance of the progress of the movement, due to the induced magnetization generated by an external magnetic field on the constituent parts of said movement, many of which are made of steels or other ferromagnetic metal alloys. These magnetic disturbances are particularly critical at the level of the movement regulator or its escapement mechanism, which are the determining functions in the counting of the current time. This phenomenon is well known to those skilled in the art.

[0004] Various solutions have been proposed in the state of the art for reducing or even eliminating the effects of external magnetic fields on a mechanical timepiece movement. These solutions mainly consist of the use of non-magnetic alloys, such as austenitic stainless steels, for the production of the various moving parts of the movement, or of non-metallic materials such as silicon or, more recently, carbon, for the realization of the oscillator of the body regulating the movement (hairspring of a sprung balance, oscillator with bistable blades for example) and / or of the escapement mechanism.

[0005] These solutions, all of which are satisfactory in terms of resistance to magnetic disturbances, are not, however, devoid of drawbacks.

[0006] In fact, austenitic steels are more difficult to process than conventional martensitic steels, for example of the 20AP type, to make them sufficiently hard and resistant to the friction forces specific to watch pivots.

[0007] Materials such as silicon, for their part, require the implementation of microtechnical manufacturing techniques by deep etching, in particular of the DRIE type, for "Dry Reactive Ion Etching", which are not only expensive and complex to implement. , but also quite harmful to the environment due to the reagents they use. In addition, the parts produced are extremely fragile to impacts and cannot be taken back by conventional machining techniques in the event of manufacturing defects. This therefore results in significant rejections and therefore additional costs.

[0008] The development of carbon balance springs is also extremely complex and costly.

Disclosure of the invention

[0009] The aim of the present invention is to overcome all or part of the drawbacks mentioned above by providing a mechanical watch mechanism with reduced sensitivity to magnetic fields capable of being manufactured using conventional manufacturing and machining techniques and of metallic materials. at contained and competitive costs with the costs of commercial movements of the ETA 2824 or Sellita SW 200 type.

To this end, the invention relates to a mechanical watch movement, comprising, arranged in kinematic connection with each other, a source of mechanical energy, a cog, an escape mechanism and a regulating member. sprung balance type, each comprising at least one mobile mounted to pivot on a plate and / or bridge, each mobile comprising a metal pivot at at least one of its ends, characterized in that the pivot of the regulating member consists of a non-magnetic or paramagnetic metal alloy, in particular but not exclusively based on copper, in order to limit its sensitivity to magnetic fields, and in that the hairspring of the regulating member is also made of a non-magnetic or paramagnetic metal alloy in order to limit its sensitivity to magnetic fields.

According to one embodiment, the pivot (s) of the escape mechanism, in particular an anchor pivot and / or an escape pinion, is (are) made of an alloy non-magnetic or paramagnetic metallic, in particular but not exclusively of copper, in order to limit its (their) sensitivity to magnetic fields.

[0012] According to one embodiment, the metal alloy of the pivots of the regulator member and of the exhaust mechanism is identical.

[0013] According to one embodiment, the magnetic intensity for stopping the movement in any orientation parallel or perpendicular to the axes of said pivots is greater than 3000 Gauss.

[0014] According to one embodiment, said non-magnetic or paramagnetic metal alloy constituting at least said regulator pivot is a copper-beryllium or phynox alloy.

According to one embodiment, said copper-beryllium alloy comprises at least 1.8% by mass of beryllium, at least 0.2% by mass of Co + Ni, at most 0.4% of Fe, at most plus 0.6% Pb, at most 0.5% impurities, the rest 100% Cu

[0016] According to one embodiment, said non-magnetic or paramagnetic metal alloy constituting the balance spring of the regulating member consists of a superconducting metal alloy, in particular based on Niobium.

[0017] The invention also relates, according to a second object, to a timepiece comprising a watch movement as previously presented.

Brief description of the drawings

Other details of the invention will emerge more clearly on reading the following description, made with reference to the accompanying drawings in which: FIG. 1 represents a perspective view of a regulator of the sprung balance type (of which only the balance is shown) and of an escapement mechanism of a watch movement according to the present invention, Figure 2 shows a left view of the elements shown in Figure 1; FIG. 3 represents comparative test measurements of stopping and of residual effects on movement in accordance with the invention according to various orientations of the magnetic field.

Embodiment of the invention

In the present description, the term “non-magnetic” material means a paramagnetic or diamagnetic or antiferromagnetic material, the magnetic permeability of which is less than or equal to 1.01.

A copper alloy is an alloy containing at least 50% by weight of copper.

The invention relates to a timepiece movement conventionally comprising a regulator member 1 of the spring-balance type including at least the pivots 12, 13 of the balance axis 11, and preferably the balance axis 11 in its entirety, are made of a non-magnetic metal alloy, and preferably copper-beryllium or Phynox. For the purposes of the present invention, the term “copper-beryllium alloy” means any alloy of the CuBe2 type, for example.

In addition, the hairspring associated with the balance 10 of the movement of the invention is also made of a non-magnetic metallic material, in particular a superconductive metallic alloy based on Niobium. In Figures 1 and 2 the hairspring associated with the balance 10 is not shown for the sake of clarity of representation. It can however be of any type conventionally known to the watchmaker and paired with the balance 10 according to conventional watchmaking techniques, provided that its constituent metallic material is itself non-magnetic. The hairspring could in particular be made of a non-magnetic metal alloy, as defined above.

The regulator member 10 is associated with an escape mechanism 2, intended to distribute to the regulator member, on a regular basis, the mechanical energy transmitted from an elastic energy source comprising for example one or more barrels (not shown) by means of the cog, as in any mechanical watch movement.

The escape mechanism 2 is for example a Swiss lever escape mechanism, the most commonly used to date. It comprises an escapement mobile 20 mounted in rotation around an axis 21 provided with two pivots 22, 23 at its ends, said pivots being received respectively on stones on a plate or a bridge of the movement. A pinion 24 for coupling the escapement mobile 20 to the movement finishing train is driven on the axle rod 21. The escape mobile 20 cooperates with an escape anchor 30 in order to periodically distribute the movement. motive energy from the energy source to the regulating organ. The anchor 30 is also freely pivotally mounted by an axis 31, the end pivots 32, 33 of which are housed on stones in a plate or a bridge of the movement. The anchor 30 cooperates by two lifts or input and output vanes with the teeth of the exhaust mobile according to the alternations of the regulating member 1, in a manner perfectly known to those skilled in the art. The regulator 1 for its part interacts with each of its alternations with the fork of the anchor 30 by a pin driven out on a large plate 34 mounted integral with the balance axis 11. A small plate 35, in which is formed a notch in which the escape pin extends, acts as an escape safety device so as to prevent the anchor 30 from overturning, again in a manner well known to those skilled in the art. The various constituent elements of the escapement mechanism 2, in particular the escapement mobile 20 and the anchor 30 preferably consist of materials customary in watchmaking, in particular steel or silicon for example, their axes 21, 31 being preferably made of a non-magnetic metal alloy such as CuBe2.

[0025] The mechanical movement of the invention exhibits, in a particularly advantageous manner, properties of resistance to disturbances from external magnetic fields. These properties are surprisingly achieved according to the invention by the sole provision of balance pivots 12, 13 made of copper-beryllium alloy and a balance-spring made of non-magnetic metallic material. Obviously, the performance of resistance to magnetism can be further improved. improved by the provision of pivots 22, 23; 32, 33 and / or pivot pins 21, 31 of the escape wheel set 20 and of the anchor 30 also made of a copper-beryllium alloy like the balance pin 11. This is not however strictly essential. , which makes the automatic movement of the present invention particularly economical in production compared to the magnetism resistant movements currently available.

With the magnetism induced by objects encountered on a daily basis, it is indeed essential to limit the magnetic sensitivity of the regulating member 1, in particular of the balance axis 11 and of the hairspring, under penalty of influencing the rate. of the timepiece in which it is incorporated.

The inventors have found after various tests and developments that it was possible to provide a resistance to magnetism very significantly improved without burdening the cost of manufacturing the movement by implementing a balance axis 11 and its pivots 12, 13 in a non-magnetic copper-beryllium alloy and a hairspring also in non-magnetic metallic material in order to advantageously limit its sensitivity to magnetic fields.

By way of nonlimiting example, one can use an alloy whose composition values, indicated in percentage by mass, are at least 1.8% by mass of beryllium, at least 0.2% by mass of Co + Ni, at most 0.4% Fe, at most 0.6% of Pb, at most 0.5% of impurities, the rest at 100% of Cu. Such a copper-beryllium alloy is particularly advantageous in that it provides very high resistance to fatigue, very good resistance to thermal relaxation, very good machinability, in particular compared to a Phynox alloy for example, all by providing very good mechanical strength Rm in practice between 1200 N / mm <2> and 1500 M / mm <2>, with a modulus of elasticity between 125 and 130 kN / mm <2>. It also has a very good basic hardness greater than 400 Vickers, which can be increased in practice up to 900 Vickers by chemical nickel plating, well known to those skilled in the art.

Various comparative tests were carried out in order to demonstrate the potentialities of the mechanical movement of the present invention. These tests are presented and discussed in relation to the table of FIG. 3. In this table, the movement of the invention is referenced O400. The limit magnetic field for stopping the movement was measured according to three orthogonal orientations (3h-9h; 6h-12h; dial-back) according to different configurations of the movement, with balance axes, mobile escapement, and / or anchor, i.e. 20AP steel, or non-magnetic copper-beryllium alloy. In all cases except one, the hairspring associated with the movement balance was a hairspring made of non-magnetic metallic material, in particular a hairspring made of a superconducting metal alloy based on Niobium-titanium. The performance of the movement of the invention O400 has been compared to that of a commercial ETA 2892 movement, which will be taken as a “witness”. We have also determined the residual effects obtained by the different configurations of movements to evaluate the persistence of the magnetic disturbance of a magnetic field on the course of the movement after leaving the magnetic field.

We can first of all note that the movement of the invention intrinsically presents, thanks to the provision of the non-magnetic metal hairspring, greater resistance to magnetism than the control movement. In fact, the limits for stopping the movement with the balance axles, anchor and escape pinion made of 20AP steel are thus more than 10 times greater in all orientations than those of the control movement.

We then see that the procuration of a copper-beryllium CuBe pivot pin for the exhaust pinion or the anchor rod only does not significantly modify the performance of resistance to magnetism of the movement compared to axes in AP20 steel. On the other hand, as soon as the movement's balance axis is made of copper-beryllium alloy, there is a very significant increase in the limit for stopping the movement in all directions of the magnetic field, to reach stop values. greater than 3000 Gauss, upper limit of measurement of the test equipment used.

Furthermore, the implementation of non-magnetic metal alloy pivot pins, in particular CuBe2, in association with a non-magnetic metal hairspring, considerably reduces the residual effect of the magnetic field on the movement compared to the Control movement. No residual effect was thus observed on the movement of the invention when the latter was subjected to a magnetic field equal to 50% or 75% of the magnetic field for stopping the control movement.

The procuration of a non-magnetic metal balance axis, associated with a non-magnetic metal balance spring, is sufficient to considerably increase the resistance to magnetism of the movement without requiring more modifications thereof in comparison to the same movement including all the axes of the movement. assortment parts (regulator and exhaust) are made of steel. In addition, the provision of all the assortment axes (balance, escapement, anchor) in CuBe2 does not provide any additional significant increase in the resistance to magnetism of the movement.

On the other hand, the use of a non-magnetic hairspring (conventional hairspring) has a very significant negative effect on the resistance to the magnetic field in the dial-back direction, that is to say in a direction of magnetic field perpendicular to the median plane of motion.

The tests thus carried out make it possible to validate the design choices of the watch movement of the invention in order to very significantly improve the performance of resistance to magnetism of a watch movement by minimally modifying the structural elements thereof with respect to the classic commercial movements, making it possible to obtain movements resistant to magnetic fields at contained manufacturing costs.

Furthermore, Figure 3 above does not fully demonstrate the effects of synergy between the combination of a hairspring made of a non-magnetic or paramagnetic alloy, particularly effective in terms of magnetic shielding along the axis dial-bottom, and at least the balance axis made of an alloy of the same type, that is to say non-magnetic or paramagnetic, particularly effective in terms of magnetic shielding in the plane of the balance-spring, of which the effects were measured in each of the main axes (that is to say respectively 3h-9h and 6h-12h), and this because of the upper limit of measurement of the test equipment used mentioned above (3000 Gauss). However, it has been established that such a combination makes it possible to obtain stop values greater than 4500 Gauss according to all of the aforementioned magnetic field orientation components. In any case, only such a combination has been shown to be effective with respect to magnetic fields oriented about 45 degrees with respect to the plane of the hairspring - and simultaneously with respect to the axes of the mechanism (regulator, escapement, and anchor), for their part, oriented in the dial-back direction - regardless of the materials used to make the non-magnetic or paramagnetic alloys. Thus, such a combination allowing isotropic magnetic shielding is much more advantageous than any solution aimed at providing magnetic shielding respectively via the balance spring of the regulating member or of the pivot axis, in particular that of the member. regulator, taken separately.

Claims (10)

1. Mechanical watch movement, comprising, arranged in kinematic connection with each other, a source of mechanical energy, a gear train, an escapement mechanism and a regulating member of the sprung balance type, each comprising at least one mounted mobile. pivoting on a plate and / or bridge, each mobile comprising a metal pivot axis at at least one of its ends, characterized in that the pivot axis of the regulating member consists of a non-magnetic or paramagnetic metal alloy in order to to limit its sensitivity to magnetic fields, and in that the balance spring of the regulating member is also made of a non-magnetic or paramagnetic metal alloy in order to limit its sensitivity to magnetic fields. 2. Watch movement according to claim 1, characterized in that the axis (s) of pivoting of the escapement mechanism, in particular an anchor pivot and / or an escape pinion, is (are) constituted ( s) a non-magnetic or paramagnetic metal alloy in order to limit its (their) sensitivity to magnetic fields. 3. Watch movement according to one of claims 1 and 2, characterized in that the metal alloy of the pivot pins of the regulator member and of the escape mechanism is identical. 4. Watch movement according to one of claims 1 to 3, characterized in that the magnetic intensity of stopping the movement in any orientation parallel or perpendicular to the axes of said pivots is greater than 3000 Gauss. 5. Watch movement (1) according to one of the preceding claims, characterized in that said non-magnetic or paramagnetic metal alloy constituting said regulator member pivot axis at least is a Phynox alloy. 6. Watch movement (1) according to one of the preceding claims, characterized in that said non-magnetic or paramagnetic metal alloy constituting said regulator member pivot axis at least is a copper-beryllium alloy. 7. Watch movement (1) according to one of the preceding claims, characterized in that said non-magnetic or paramagnetic metal alloy constituting said pivot axes of the escapement mechanism is a Copper-Beryllium or Phynox alloy. 8. Watch movement (1) according to claim 6 or 7, characterized in that said copper-beryllium alloy comprising at least 1.8% by mass of beryllium, at least 0.2% by mass of Co + Ni, at least. plus 0.4% Fe, at most 0.6% Pb, at most 0.5% impurities, the rest 100% Cu. 9. Watch movement (1) according to one of the preceding claims, characterized in that said non-magnetic or paramagnetic alloy constituting the balance spring of the regulating member consists of a superconducting metal alloy, in particular based on Niobium. 10. Timepiece comprising a movement according to one of claims 1 to 9.