CH719496A2 - Device for guiding a rotation shaft of a spiral balance. - Google Patents

Abstract

The device (1) according to the invention is intended to guide a rotation shaft (6) of a spiral balance. The device comprises at least the rotation shaft and a guide bearing (2) of one end of the rotation shaft of the spiral balance, the guide bearing comprising at least one blade (3) and a surface (5) contact and maintenance of the end of the rotation shaft of the spiral balance. At least one end part of the shaft and at least the blade and the contact surface of the guide bearing are made of a material whose Young's modulus is less than or equal to 100 GPa and/or the coefficient of friction of the materials of the parts in contact or of the coating of the parts in contact is less than or equal to at least 0.15.

Description

TECHNICAL AREA

[0001] The invention relates to a device for guiding a rotating shaft of a spiral spring balance of a timepiece.

[0002] The invention also relates to a watch movement and a timepiece respectively comprising such a device for guiding a rotating shaft of a spiral spring balance.

TECHNOLOGICAL BACKGROUND

[0003] In watchmaking, it is known to use a spiral balance constituting a mechanical oscillator, the oscillation frequency of which can be adjusted electronically or mechanically by a finishing train linked to a barrel system. The pivot at one end of the shaft can generally be guided by passing through a circular guide opening but with a certain clearance. Under these conditions, there is imprecise positioning and significant friction depending on the position of the watch, likely to quickly wear out said pivot and alter the chronometric precision of the watch, which constitutes a disadvantage.

Document CH 239 786 describes a device for guiding a pivot at one end of the rotation shaft of a spiral balance. The device is arranged with an olive stone and a stop inclined relative to the balance shaft. The shaft is guided without play. Friction is therefore independent of the position of the watch. In a horizontal position of the watch, the additional friction of the cylindrical part of the pivot against the olive stone is thus similar to that experienced in a vertical position. On the other hand, the amplitude is reduced for all positions, which constitutes a disadvantage for controlling precision.

[0005] It is also known from documents EP 3 258 325 B1 and CH 269 552, the production of a rotation shaft of a spiral balance, in a ceramic material so as to avoid too rapid wear of the ends of the rotating shaft in a guide.

[0006] Document EP 3 382 472 A1 describes a guide bearing for a pivot of a rotation shaft of a spiral balance of a timepiece. A guide bearing may be provided on each side of the ends of the rotating shaft. The guide bearing can be constituted in one embodiment of three curved blades in the shape of a spiral regularly spaced from each other, a first end of each blade is fixed to a ring coaxial with the rotation shaft while a second end of each blade comes into contact with one end of the rotation shaft of the balance to hold it radially. The guide bearing is made of a metallic material. The guide bearing made of a metallic material does not sufficiently reduce the forces in contact with the shaft or the pivot on the shaft. Under these conditions, there is too much energy loss due mainly to friction with the end of the pivot or the rotation shaft, even if the friction no longer depends too much on the orientation of the watch, this which constitutes a disadvantage.

SUMMARY OF THE INVENTION

[0007] The main aim of the invention is therefore to overcome the disadvantages of the state of the art by proposing a device for guiding a rotation shaft of a spiral balance with limited clearance of the shaft due to gravity and with a material and geometry of the contact parts of the guide selected to reduce the support forces and therefore the friction forces.

[0008] For this purpose, the invention relates to a device for guiding a rotation shaft of a spiral balance, which comprises the characteristics defined in independent claim 1.

[0009] Particular embodiments of the device for guiding a rotation shaft of a spiral balance are also described in dependent claims 2 to 13.

[0010] Advantageously, at least the parts in contact with the shaft, or a pivot fixed to the shaft, and a guide bearing of the shaft are: – made of a material having a modulus of Young less than or equal to 100 GPa so as to reduce friction forces, and/or – made with, or coated with materials whose coefficient of friction between them is less than 0.15, or even 0.1, or even 0 .05.

[0011] Preferably, the material can be ceramic or glass or also a polymer filled or not to produce in particular the guide blade(s) and maintain the guide bearing of the device in contact with one end of the shaft rotation of the spiral balance or the end pivot of the rotation shaft. In addition to the chosen material, there must still be machining accuracy within a defined tolerance interval. The geometry of the blade(s) can also be adapted to minimize the contact surface with the end of the shaft or the pivot on the shaft.

[0012] The invention also relates to a watch movement which comprises such a device as defined in claim 14.

[0013] The invention also relates to a timepiece which comprises such a device as defined in claim 15.

BRIEF DESCRIPTION OF THE FIGURES

[0014] The aims, advantages and characteristics of a device for guiding a rotation shaft of a spiral balance will appear better in the following description, particularly with reference to the drawings in which: – Figures 1a and 1b represent a three-dimensional view from the above of a spiral balance with the device for guiding the rotation shaft of the spiral balance, and a vertical side view of the spiral balance with the device for guiding the rotation shaft according to the invention, – Figure 2 represents a simplified top view of a first embodiment of a guide bearing of the device for guiding the rotation shaft according to the invention, and - Figure 3 represents a simplified top view of a second form of execution of a guide bearing of the device for guiding the rotation shaft according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, all the components or elements of the device for guiding a rotation shaft of a spiral balance are known in general. These elements or components will therefore only be described briefly. It should first be noted that the device for guiding a rotation shaft of the spiral balance also includes said shaft which is part of a whole with the guiding elements of this shaft and means for avoiding the effect of gravity. Of course, mention may also be made of an assembly which comprises at least one guide bearing and the rotation shaft of the spiral balance to define the device for guiding a rotation shaft of the spiral balance.

[0016] In the following description of the device for guiding a rotation shaft of a spiral balance, a guide bearing may be provided, which may consist of contact parts such as flexible blades for example for the positioning of the balance spring axis. This makes it possible in particular to limit parasitic movements of the hairspring balance, when the movement is in a horizontal position. In general, the movements caused are responsible for chronometric faults. In one embodiment with flexible blades, these blades have a centering effect on the axis of rotation of the spiral balance.

[0017] It is also possible according to the invention to balance the friction forces between horizontal and vertical positions of the watch movement. Losses due to friction are generally responsible for drops in amplitude and therefore for differences in timing in chronometry due to the intrinsic anisochronism of the spiral balance system. If we have equivalent losses regardless of the horizontal or vertical position, this makes it possible to guarantee good precision of the movement whatever its position in space.

[0018] According to the present invention, it is also possible to imagine a pivoting system in a closed space, which allows the use of a lubricant unlike what is described in the prior art where we encounter a so-called open system. , which is generally incompatible with lubrication. With an added lubricant, this makes it possible to limit friction losses as much as possible, which provides the advantage of integrating guide bearing blades, which can be stiffer but also more easily manipulated when assembling the components.

[0019] As also described below according to the present invention, there is an advantage of being able to use components made of polymer materials. These components are for example produced for flexible or elastic blades in a guide bearing or also for the coating of contact parts of such guide bearings. Instead of flexible or elastic blades or contact parts, it can also be imagined to use an elastomer provided with friction surfaces made of a material more suited to friction with suitable inserts.

Figures 1a and 1b represent the spiral balance with the device 1 for guiding the rotation shaft assembly 6 of said spiral balance. The spiral balance is formed of a serge 12 connected for example by three arms 15 to a central rotation shaft 6, and a spiral spring 13, having a first end connected to a not shown pin of a balance bridge. A second end of the spiral spring 13 is fixed directly, or indirectly via a ferrule, on the rotation shaft 6 of the spiral balance.

The device 1 for guiding the rotation shaft 6 of the spiral balance comprises said rotation shaft 6 and at least one guide bearing 2 preferably disposed at one end of the rotation shaft 6. Of course, it is entirely conceivable to have two guide bearings 2 of the rotation shaft arranged at both ends of the rotation shaft in particular to center the rotation shaft 6 along the central axis AC.

The guide bearing 2 can advantageously be mounted at an upper end of the rotation shaft 6, for example on the dial side. However, it can be envisaged to have two guide bearings 2 mounted respectively at each end of the rotation shaft 6. Each guide bearing 2 described in more detail with reference to Figures 2 and 3 below, comprises parts of contact and maintenance of the ends of the rotation shaft or end pivots of the rotation shaft given that the rotation shaft linked to the spiral balance is always in alternating rotation in normal operation relative to the guide bearing 2 which is fixedly mounted in or on an adjustment member not shown.

[0023] At least all the parts in contact with the guide bearing 2 and the rotation shaft 6 or the end pivot of the rotation shaft are advantageously made of a material whose modulus of elasticity (modulus of elasticity Young) is less than or equal to 100 GPa and/or have the lowest possible friction coefficient, for example at least less than or equal to 0.15. Preferably, the material may be ceramic, glass or a charged or unfilled polymer and a list of these materials will be given in more detail in the second part of the detailed description.

[0024] Figure 2 represents a first embodiment of the guide bearing 2 of the rotation shaft 6 linked to the spiral balance. The general shape of the guide bearing 2 is generally cylindrical on the periphery to be housed and fixed in an opening of an adjustment or mounting plate not shown. In a central part of the guide bearing 2 where the guiding and holding of the rotation shaft 6 will take place, at least one guide blade 3 is provided to come into contact at one of its ends 4 with the rotation shaft 6 or on an attached part of the rotation shaft, which may be a pivot.

[0025] According to the invention in this first embodiment, at least one guide bearing 2 comprises, on a first side of the central axis AC, a support part 5, which is a support surface 5 of any geometric shape adapted to make point contact or on a contact line with the rotation shaft 6 or the pivot mounted on the rotation shaft. The support surface can also be made in the shape of a V or a pad, or the like, and is arranged to center the axis of rotation of a shaft 6 on a plane bisecting the support surface 5. This surface d The support 5 is symmetrical. The same guide bearing 2 comprises, on a second side of the axis of revolution, which is opposite the first side, at least one holding element 4 at the free end of the blade 3, which is arranged substantially diametrically opposite the support surface 5. It is understood that the support surface 5, symmetrical with respect to its bisecting plane, comprises two elementary support surfaces, of the V-shaped surface in this case.

According to the invention, all the holding elements 3, 4 with the contact surface 40 are arranged to exert on a shaft 6 a resulting elastic return force directed towards the central axis AC, and to prevent a radial exit , outside this guide bearing 2, a shaft 6 inserted axially in the direction of the axis of revolution in this same guide bearing 2.

However, it should be noted that a single blade 3 having a contact surface 40 to hold the rotation shaft against the V-shaped surface 5 is difficult to produce because depending on the orientation of the timepiece the spiral balance is too heavy to be held by the single blade provided.

[0028] In Figures 2 and 3, the blade 3 up to its free end is of rectangular cross section so as to have a flat contact portion 40 in contact with the end of the shaft 6 or the pivot 6' on a contact line. As a variant, at least the free end of the blade 3 has a lenticular section geometry to have only one point of contact on the portion 40 in order to reduce friction in contact with the end of the shaft rotation 6 or the pivot mounted on the rotation shaft 6.

It should be noted that contact can be imagined between the shaft 6 or the pivot and one or more supporting parts 5 in point form or along a contact line. For point contact, each support part 5 can be produced for example in the form of a convex structure or portion of a ball. However, many other structures can be imagined to have such punctual contact. For contact along a contact line, it may also be a cylindrical structure or portion of a support part arranged along an axis parallel to the axis of rotation of the rotation shaft or any other structure. It can be imagined a combination of point contact or along a line of contact. In addition, any geometric shape can be proposed to make point contact or on a contact line with the rotation shaft or the pivot mounted on the rotation shaft

[0030] For further information on this first embodiment, reference may be made to patent application CH 716 957 A2 in particular from paragraph [0021] to paragraph [0027], which describes guide bearings of a time indicator tree.

[0031] Figure 3 represents a second embodiment of the guide bearing 2 of the device 1 for guiding the rotation shaft 6 of the spiral balance. This guide bearing 2 can comprise at least one contact blade 3 and two support parts 5, which are preferably two other contact blades 3. Thus, the guide bearing 2 is composed of a peripheral ring and three blades 3 in the form of turns to move in the direction of the rotation shaft 6 to come into contact with the rotation shaft 6 in order to hold it and guide it along the central axis AC. The free end 4 of each blade 3 comes into direct contact with the rotation shaft 6 to hold it, center it and guide it along the central axis AC. The three blades 3 can be of another shape and section other than rectangular than those of the turns. For example, each blade is rectilinear arranged angularly and regularly spaced 120° from one another to each contact the rotation shaft regularly. It can still be envisaged to have more than three contact blades with the rotation shaft.

The guide bearing 2 of this second embodiment can be obtained in single-piece form in a ceramic material, glass or filled or unfilled polymer, in particular below the limit threshold of the modulus of elasticity less than or equal to at 100 GPa and/or have the lowest possible coefficient of friction, for example at least less than or equal to 0.15. Both the part of the rotation shaft 6 in contact with parts of the guide bearing 2 are made of the same material or a different material or coating fulfilling the conditions defined by the threshold of the modulus of elasticity or having a coefficient of friction as low as possible, for example at least less than or equal to 0.15.

[0033] For further information on this second form of execution, reference may be made to patent application EP 3 396 470 A1 from paragraph [0018] to paragraph [0022].

As the type of ceramics to be used for the guide bearing and/or the rotation shaft, it may be ceramics based on oxides, mainly alumina and zirconia, or silica.

[0035] Concerning zirconium oxide (ZrO2), it can be used in zirconia stabilized with yttrium oxide (ZrO2+Y2O3), which have a metastable tetragonal crystal structure, a grain size less than 0, 50 µm, a density greater than 6.00 g/cm<3> and a hardness of approximately 1200 HV. Zirconia can also be stabilized with cerium oxide (ZrO2+ CeO2) or magnesium oxide ((ZrO2+ MgO), depending on the properties of the desired final material.

[0036] Concerning Alumina Zirconia, the composites are generally 80% 3Y-TZP / 20% Al2O3 (ATZ) or 90% Al2O3 / 10% 3Y-TZP (ZTA), combining the properties of aluminas and high purity zirconia to obtain final characteristics that offer the best of each material.

[0037] It should also be noted that the use of hard materials makes it possible to reduce or reduce the contact friction forces of the materials in contact, which can also be sought.

[0038] From the description which has just been made, multiple alternative embodiments of the device for guiding a rotation shaft of a spiral balance can be designed by those skilled in the art without departing from the scope of the invention. defined by the claims.

Claims (15)

1. Device (1) for guiding a rotation shaft (6) of a spiral balance, the device comprising at least the rotation shaft (6) and at least one guide bearing (2) of one end or 'a pivot (6') fixed to one end of the rotation shaft (6) of the spiral balance, the guide bearing comprising at least one blade (3) and at least one contact part (5) and maintaining the end or pivot (6') of the rotation shaft (6) of the spiral balance, characterized in that at least one end end portion of the rotation shaft (6) or pivot ( 6'), or at least the contact parts (3, 5) of the guide bearing (2) are made of a material whose Young's modulus is less than or equal to 100 GPa and/or the coefficient of friction of the materials of the parts in contact or the coating of the parts in contact is less than or equal to at least 0.15. 2. Device (1) according to claim 1, characterized in that the support part (5) is a support surface (5) of any geometric shape adapted to make point contact or on a contact line with the rotation shaft (6) or the pivot mounted on the rotation shaft (6). 3. Device (1) according to claim 2, characterized in that the support part (5) is a support surface (5) 4. Device (1) according to claim 1, characterized in that two support parts (5) are made up of contact blades (3) to have three contact blades to ensure centering of the axis of rotation of the balance hairspring. 5. Device (1) according to claim 4, characterized in that it consists of three contact blades (3), said three blades each being in the shape of a turn, and in that a first end of each blade is fixed to a coaxial ring (2) to the rotation shaft (6) while a second end (4) of each blade comes into contact with one end of the rotation shaft (6) of the balance to hold it axially. 6. Device (1) according to claim 4, characterized in that the contact blades (3) are each of rectilinear shape, and in that a first end of each blade is fixed to a coaxial ring (2) at the rotation shaft (6) while a second end (4) of each blade comes into contact with one end of the rotation shaft (6) of the balance to hold it axially. 7. Device (1) according to one of claims 5 and 6, characterized in that all the blades are regularly spaced from one another by 120° over one revolution of the ring. 8. Device (1) according to one of the preceding claims, characterized in that at least one blade (3) or a support part (5) comprises a contact portion against the shaft (6) or the pivot (6') formed so as to have only one point of contact with the shaft (6) or the pivot (6'). 9. Device (1) according to one of claims 1 to 7, characterized in that each blade (3) comprises a contact portion against the shaft (6) or the pivot (6') formed to have only 'a single point of contact to reduce friction. 10. Device (1) according to claim 1, characterized in that a contact part of the shaft (6) and the contact blade (3) and the support part (5) are made of the same material ceramic or glass or filled or unfilled polymer. 11. Device (1) according to claim 1, characterized in that a contact part of the shaft (6), and the contact blade (3) and the support part (5) of the guide bearing ( 2) are made of two different materials in ceramic or glass or in charged or unfilled polymer. 12. Device (1) according to one of claims 10 and 11, characterized in that the elements of the guide bearing (2) are in one piece. 13. Device (1) according to claim 1, characterized in that the coefficient of friction of the materials of the parts in contact or of the coating of the parts in contact is less than or equal to at least 0.1, or even less than or equal to at least 0.05 or at least one end part of the shaft (6) or the pivot (6') or at least the contact parts (3, 5) of the guide bearing (2) are made of a material of which the Young's modulus is less than or equal to 100 GPa. 14. Timepiece movement, for example a wristwatch, equipped with such a device (1) according to one of the preceding claims. 15. Timepiece, for example a wristwatch, provided with a movement equipped with such a device (1) according to one of the preceding claims.