Assembly including timepiece shaft and at least one guide

Abstract

To provide a hard and sturdy timepiece shaft whose manufacturing process is simplified.SOLUTION: A timepiece shaft 1, especially a balance staff 1, comprises a first functional portion 2a, 2b including at least one part 221a, 221b of a pivot-shank 22a, 22b and / or at least one part 211a, 211b of a pivot 21a, 21b, where the first functional portion 2a, 2b is made of ceramic, and a first outer diameter D1 of the first functional portion 2a, 2b is less than 0.5 mm, or less than 0.4 mm, or less than 0.2 mm, or less than 0.1 mm.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a clock shaft, particularly a balance staff. The present invention also relates to an oscillator or a small clock movement or a clock including such a shaft.

Background Art

[0002] The balance staff is an important part of the clock regulating mechanism. The balance staff includes, at both ends thereof, pivot barrels extended by pivots. The balance staff particularly holds the hairspring and oscillates on its pivots within bearings. The pivot barrels and pivots of the shaft, which constitute regions of low mechanical strength, are designed to absorb force by means of play when impacted. Nevertheless, in certain cases, particularly under high-intensity impacts, due to its small dimensions, especially its small diameter, the pivot may be damaged by its respective bearings.

[0003] For this reason, the shaft is - to have a high elastic limit so as not to plastically deform when subjected to a large impact, - to be sufficiently robust so as not to break when subjected to a large impact, and - to have sufficient hardness, particularly in the region of the pivots, so that the shaft is not worn or destroyed by daily impacts due to its constant movement, and so that the shaft optimizes the quality factor and isochronism of the clock of which it forms part. is required.

[0004] The clock shaft has conventionally been cut from 20AP steel and then forged. The pivot is then rolled in order to obtain the required surface condition and surface hardness. The hardness typically achieves at least 700 HV. Whether hardened or not, shafts made of 20AP steel or other metal materials require the rolling operation in the area of the pivot in order to guarantee the machining accuracy of the pivot, its wear over time, its durability against scratches and impacts, and also to guarantee the optimal operation of the movement by controlling the tribological parameters. The operation consisting of the grinding and surface hardening steps on the surface of the pivot is complex and delicate, and requires a high level of skill from the technician performing the operation. Furthermore, 20AP steel contains lead (0.2% by weight) and needs to be replaced in the near future with lead-free steel such as FinemacTM (or 20C1A). The manufacture of such shafts is similar. The shaft is cut from a bar before forging and then heat-treated and forged to improve its hardness. Annealing for stress relief removes the internal stress and can prevent the shaft from breaking like glass when subjected to an impact. The main defect of this steel is the lack of hardness in the area of the pivot, which requires the rolling operation to obtain the required final properties. Also, shafts made of 20AP or Finemac steel are ferromagnetic, and if the movement containing them is exposed to a magnetic field, residual magnetization may cause interference in the operation of the movement.

[0005] The shafts of 20AP or Finemac steel can be replaced by shafts of austenitic steel hardened by carbon or nitrogen ion implantation, or austenitic alloys based on cobalt or nickel. These shafts are also rolled to improve their properties. According to Patent Document 1, the shaft is made of 316L type austenitic stainless steel for the purpose of minimizing sensitivity to the magnetic field, but the resulting strength and hardness do not reach the characteristics required to ensure wear resistance. Solutions applying DLC (diamond-like carbon) type coatings have been considered, but a significant risk of delamination has been confirmed. Similarly, surface treatment by nitriding or carburizing for the purpose of forming chromium carbide or chromium nitride, although the intended effect is obtained with respect to surface hardening, is accompanied by a decrease in corrosion resistance, which is harmful to the quality of the parts and products. Patent Document 1 discloses a solution for hardening austenitic steel, austenitic cobalt alloy or austenitic nickel alloy by thermochemical treatment for the purpose of bonding carbon or nitrogen atoms located in the interstitial positions of the crystal lattice of the alloy, while restricting the risk of corrosion of the shaft and strengthening the material before performing the rolling of the pivot. The hardness achieved thereby is close to 1000 HV, and this type of part will theoretically be placed at a higher level than a part made of 20AP steel.

[0006] However, such shafts require rolling in the pivot area to obtain the final dimensions and, in particular, to obtain a surface condition that enables appropriate performance in terms of the timing that must be achieved. For this reason, this solution is not optimal because it requires at least two treatment steps, namely a surface hardening step followed by a second rolling step, for the shaft.

[0007] The alternative disclosed in Patent Document 2 that does not require rolling consists of making all or part of the shaft and, in all cases, the pivot or pivots, from a metal material (metal matrix composite or MMC) hardened with hard ceramic particles. This material has a hardness of 1000 HV or more and is partly composed of particles with a size of 0.1 to 5 microns. An example of the material is 92% tungsten carbide (WC) particles integrated in a nickel matrix, which is adjusted before being injected into a mold in the shape of a shaft. After injection, the obtained raw material is sintered, and then the shaft is polished using diamond paste, especially in the area of the pivot. A shaft with a metal matrix consisting of 92% WC and 8% nickel has a toughness of 8 MPa·m 1 / 2 and a hardness exceeding 1300 HV. Considering the typical dimension of the pivot of about 60 microns and also the importance of concentricity and surface condition, the use of composite materials containing particles that tend to separate can pose a risk. In fact, regarding the wear behavior of this type of material, there is only a very small margin in the dimensions of small watch manufacturing. The separation of the reinforcing particles can affect the shape integrity of the pivot or pivots.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] The object of the present invention is to provide a watch shaft that can eliminate the above-mentioned drawbacks and improve the watch shaft known from the prior art. In particular, the present invention proposes a hard and robust watch shaft with a simplified manufacturing process.

Means for Solving the Problems

[0010] For this purpose, the clock shaft according to the present invention is defined in claim 1.

[0011] Different embodiments of the clock shaft according to the present invention are defined in claims 2 to 9.

[0012] The shaft and guide assembly according to the present invention are defined in claim 10.

[0013] Different embodiments of the assembly according to the present invention are defined in claims 11 and 12.

[0014] The oscillator according to the present invention is defined in claim 13.

[0015] The small clock movement according to the present invention is defined in claim 14.

[0016] The clock according to the present invention is defined in claim 15.

[0017] The accompanying drawings represent, by way of example, three embodiments of the clock shaft according to the present invention, different embodiments of the system according to the present invention, and an embodiment of the clock according to the present invention.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

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Figure 9

DETAILED DESCRIPTION OF THE INVENTION

[0019] An embodiment of the timepiece 120 will be described with reference to FIG. 1. The timepiece is, for example, a small timepiece, particularly a wristwatch. The timepiece includes a small timepiece movement 110, particularly a mechanical movement. The small timepiece movement includes an oscillator 100, particularly a spring template 8 oscillator. The template is, for example, fitted into Tianzhen 1.

[0020] Tianzhen 1 has first functional parts 2a, 2b including the following. - At least a part 221a, 221b of the pivot bodies 22a, 22b, and / or - At least a part 211a, 211b of the pivots 21a, 21b. The first functional part is made of ceramic and has a first outer diameter D1 of less than 0.5 mm, or less than 0.4 mm, or less than 0.2 mm, or less than 0.1 mm, for example, the maximum outer diameter.

[0021] In the first embodiment shown in FIG. 1, the shaft 1 has a first pivot 21a, a first pivot body 22a, a portion 33 for receiving the plate 9, a base 34 for receiving the template 8, a portion 32 for receiving the template 8, a portion 31 for receiving the hook ball of the scroll (not shown), a second pivot 21b, and a second pivot body 22b. Advantageously, the pivot body portion has a dimension exceeding 0.1 mm, or exceeding 0.2 mm, or exceeding 0.25 mm in at least one direction or in all directions. Advantageously, the pivot portion has a dimension exceeding 0.04 mm, or exceeding 0.05 mm, or exceeding 0.1 mm in at least one direction or in all directions. Preferably, the first pivot body portion has a longitudinal piece of the pivot body (or at least the outer surface of the piece of the pivot body) having a length of at least 0.2 mm. Preferably, the first pivot portion has a longitudinal piece of the pivot portion (or at least the outer surface of the piece of the pivot) having a length of at least 0.1 mm.

[0022] In the first embodiment shown in FIG. 1, the shaft 1 has two first functional portions 2a and 2b, and each of the first functional portions includes the following. - At least a part 221a, 221b of the pivot bodies 22a, 22b, and / or - At least a part 211a, 211b of the pivots 21a, 21b. In the first embodiment shown in FIG. 1, the two functional portions are made of ceramic, and each of the two first functional portions has a first outer diameter D1, for example a maximum outer diameter, of less than 0.5 mm, or less than 0.4 mm, or less than 0.2 mm, or less than 0.1 mm.

[0023] The first functional portion can provide various functions, and in particular the following functions can be provided. - In particular, a guiding function in a turning and / or translational movement, that is, the portion has a contact surface, in particular a guide, with other parts in order to ensure a turning and / or translational movement, the portion and the other parts are in contact and perform a relative movement, and / or - The receiving function, i.e., this part has a contact surface with other parts to ensure the positioning and / or holding of other parts to this part, and / or - The meshing function, i.e., this part has a contact surface with a tooth shape between this part and other parts to ensure the meshing between this part and other parts, and / or - The force transmission or force absorption function, i.e., this part is mechanically stressed.

[0024] In the first embodiment shown in FIG. 1, the first and second pivots 21a, 21b provide a pivoting function and a force absorption function in case of shock or generally when the watch including the axis is accelerated. The first and second pivot bodies 22a and 22b provide a force absorption function when receiving shock or generally when the watch including the axis is accelerated.

[0025] The axis may also have a second functional part 3, in particular, - Second functional parts 31, 32, 33 and 34 for receiving watch parts, in particular the temple 8, the plate 9, the hairspring bobbin, or a gear or other axes 6 in other embodiments described later, or - In other embodiments, a second pivoting part of a watch part such as a gear on the axis, which permits pivoting of the watch part with respect to the axis of the watch part, or - A second meshing part, in particular in other embodiments, a tooth row, may be provided.

[0026] In the first embodiment shown in FIG. 1, the parts 31, 32, 33 each provide a receiving function.

[0027] Advantageously, the second functional part has a second outer diameter D2, for example a maximum outer diameter, of less than 2 mm, or less than 1 mm, or less than 0.5 mm. Preferably, the second functional part is made of ceramic.

[0028] More advantageously, the ratio of the dimension of the first diameter to the dimension of the second diameter is less than 0.9, or less than 0.8, or less than 0.6, or less than 0.5, or less than 0.4.

[0029] The fact that the first functional part and / or the second functional part is made of ceramic means that the functional part is completely made of ceramic. Preferably, it is excluded to realize the functional part with a material formed by adhering ceramic particles with a non-ceramic matrix such as a metal matrix. "Ceramic" is understood to mean a homogeneous or substantially homogeneous material, including the microscopic level. Preferably, the ceramic is homogeneous over a distance exceeding 6 μm, or 10 μm, or 20 μm in at least one direction or in all directions. Preferably, the ceramic does not contain non-ceramic materials over a distance exceeding 6 μm, or 10 μm, or 20 μm in at least one direction or in all directions.

[0030] Advantageously, the first functional part has a dimension exceeding 20 μm, or 40 μm, or 50 μm in at least one direction or in three mutually perpendicular directions, and / or the first functional part has the same diameter as the diameter of the axis in the region of any point of the first functional part, and / or the first functional part is located between two planes perpendicular to the axis of the shaft shape.

[0031] Advantageously, the second functional part has a dimension exceeding 20 μm, or 40 μm, or 50 μm in at least one direction or in three mutually perpendicular directions, and / or the second functional part has the same diameter as the diameter of the axis in the region of any point of the second functional part, and / or the second functional part is located between two planes perpendicular to the axis of the shaft shape.

[0032] Advantageously, the ceramic consists (by weight or mole) mostly or mainly of - zirconium oxide, and / or - alumina composed of.

[0033] For this reason, zirconium oxide and / or alumina may be a dominant element in the ceramic. However, the weight or molar ratio of zirconium oxide and / or alumina may be less than 50%.

[0034] Optionally, the ceramic may contain one or more of the following elements in addition to zirconium oxide and / or alumina. - Carbon nanotubes, - Graphene, - Fullerenes, - Yttrium oxide, - Cerium oxide, - Zirconium carbide, - Silicon carbide, - Titanium carbide, - Zirconium boride, - Boron nitride, - Titanium nitride, and - Silicon nitride.

[0035] Alternatively, the ceramic may consist mostly or mainly of silicon nitride (by weight or mole).

[0036] For this reason, silicon nitride may be a dominant element in the ceramic. However, the weight or molar ratio of silicon nitride may be less than 50%.

[0037] Optionally, the ceramic may contain one or more of the following elements in addition to silicon nitride. - Carbon nanotubes, - Graphene, - Fullerenes, - Zirconium oxide, - Aluminum oxide, - Yttrium oxide, - Cerium oxide, - Zirconium carbide, - Silicon carbide, - Titanium carbide, - Zirconium boride, - Boron nitride, and - Titanium nitride.

[0038] For example, the ceramic may be one of the ceramics in the following table.

[0039] [Table 1]

[0040] It may also be considered to manufacture the shaft from ceramic needles extruded using various diamond grinding wheels. After these steps, the piece is shape - conforming and can have sufficient hardness without post - processing.

[0041] Alternatively, undergoing polishing only after the steps of injection molding or pressing of the preform can optimize the process, especially through time savings in the manufacturing cycle.

[0042] Also alternatively, other manufacturing techniques, such as cold isostatic pressing (CIP) for example, can further improve the properties of the resulting piece by reducing the number of defects contained in the material before machining. In particular, this increases its toughness.

[0043] As described above, due to the inherent properties of very hard ceramics, the pivots are not damaged by impact and their performance is maintained over time. Advantageously, in the case of a significant impact, these pivots do not deform, while steel pivots may bend, thus affecting the time - measuring method of the watch. Therefore, ceramics as described above can maintain the shape conformity of the pivots over time.

[0044] Furthermore, the ceramic is non - magnetic and provides the additional advantage that it does not affect the operation of the watch when the watch is exposed to a magnetic field, especially a magnetic field exceeding 32 kA / m (400 G).

[0045] Advantageously, the entire shaft is made of ceramic. However, it is also conceivable to limit the ceramic part to a first functional part including at least one pivot and / or at least one pivot body.

[0046] Advantageously, the first part has a rotational surface, in particular a cylindrical surface, or a conical surface, or a frustoconical surface, or a surface generating a curve. The pivot body and the pivot may be fused or at least not delimited by a free edge such as a flange. For example, the pivot body and the pivot may be separated by a frustoconical surface or a surface generating a curve.

[0047] Two variants of a first embodiment of an assembly 41 including the above-mentioned shaft 1 and at least one guide 51, in particular a bearing 51, are illustrated in FIGS. 2 and 3 respectively. Here, the shaft is designed to rotate or pivot within at least one bearing.

[0048] The guide may take the form of a conventional vibration-resistant bearing. For this reason, in the first embodiment, at least one bearing 51 includes a bearing stone 511 designed to cooperate with a cylindrical or frustoconical part of the pivot 21', and a receiving stone 512 designed to cooperate with one end 212' of the pivot. These stones cooperate with the pivot 21' for pivoting and receiving, or for axial restraint of the shaft within the guide.

[0049] In a first variant of the first embodiment of the assembly, the shaft 1 includes a pivot 21' having a raised or convex end 212'.

[0050] In a second variant of the first embodiment of the assembly, the shaft 1 includes a pivot 21'' having a hollow or concave end 212''.

[0051] The fact of having a ceramic shaft, which is a hard and tough material, enables the achievement of a shape that optimizes and guarantees permanent contact in the area of the pivot and the bearing in which the pivot rotates, particularly in the area of the end of the pivot. This is difficult to achieve with conventional rolled alloys such as 20AP steel because the risk of performance degradation due to wear is more significant, especially due to very high contact pressures.

[0052] A second embodiment of the assembly 42 having the shaft 1 described above and at least one guide, particularly the bearing 52, is illustrated in FIG. 4. Here, the shaft is designed to rotate or pivot within at least one bearing. In the second embodiment, the at least one guide 52 includes a ball track 521 and balls 522, and the balls cooperate in contact with a pivot 21* having a conical end 212* to guide the shaft into the guide. Of course, alternatively, the end of the pivot 21* may have a conical table surface. The balls roll simultaneously along the ball track and the pivot.

[0053] FIGS. 6 and 7 illustrate the advantages of a rolling bearing designed to cooperate with a spring type oscillator. In fact, from FIGS. 6 and 7 obtained by measuring an oscillator cooperating with a typical vibration-resistant bearing at different clock positions and an oscillator cooperating with a rolling bearing at different clock positions, it can be seen that the operation of the oscillator cooperating with the rolling bearing has less deviation of the quality factor between different clock positions compared to the operation of the oscillator cooperating with a typical vibration-resistant bearing.

[0054] However, for the proper functioning of the pivot and the reduction of timing deviation, it is essential that the shape of the pivot remains constant over time in all pivot shapes, regardless of the forces and impacts to which the small watch is exposed. This is even more essential in certain cases. In fact, if the pivot associated with the rolling bearing is damaged or plastically deformed by an impact, many of the advantages of this solution are lost.

[0055] Therefore, using ceramic in the manufacture of the ball and pivot can optimize the use of the rolling bearing and significantly reduce the deviation of the quality factor between different watch positions taken by the watch.

[0056] A second embodiment of the watch axis 1' according to the present invention will be described with reference to FIG. 5.

[0057] The shaft 1' is designed to be provided on a pivot shaft 6, especially a pivot shaft made of different materials, especially free-cutting steel.

[0058] For this reason, the first functional part includes the pivot 2a, while the second functional part may exist in the form of a part 35 designed to be fixed, especially by driving or welding, in a hole 36 formed in the body of the pivot shaft 6.

[0059] The present invention has been described naively so far. However, the present invention is clearly applicable to other watch axes, such as small watch gears, especially the second wheel, or large intermediate wheels, or small intermediate wheels, or the pivot shaft of the second hand, which are related to the last chain of the movement of small watches.

[0060] The watch axis according to the present invention can also be implemented in the sense of optimizing the escapement of small watches, and thus can enable the pivoting of the escape wheel or the blocker or the anchor related to the escapement. Of course, the present invention is applicable to all small watch gears related to additional watch functions, such as calendars and chronographs.

[0061] In an alternative embodiment shown in FIGS. 8 and 9, the first functional part may provide a translational movement function. Here, the time axis exists in the shape of a pin 1", including the first functional part 2a existing in the shape of the pivot body 22a. The pivot body 22a cooperates with a groove 53 formed in a small watch part such as a chronograph hammer 91, for example, to guide the translational movement of the part, particularly the translational movement in the longitudinal direction of the groove. The pin 1" has a second functional part existing in the shape of a pivot body 45 designed to be driven into a hole 46 of a watchmaking ebauche 81. In this embodiment, the first and second functional parts are separated by a flange 450, particularly a seat 450.

[0062] Once formed, the ceramic piece does not require heat treatment or rolling to obtain excellent wear resistance performance.

Explanation of reference numerals

[0063] 1, 1', 1" Time axis 2a, 2b First functional part 21a, 21b, 21', 21", 21* Pivot 22a, 22b Pivot body

Claims

1. A clock set (1;1';1"), in particular a balance stem (1), having a first functional part (2a;2b) including at least a part (221a;221b) of a pivot body (22a;22b) and / or at least a part (211a;211b) of a pivot (21a;21b;21':21";21*), said first functional part being entirely made of ceramic, said first functional part having a first outer diameter (D1) less than 0.5 mm, or less than 0.4 mm, or less than 0.2 mm, or less than 0.1 mm.

2. The ceramic has a major portion comprising: Zirconium oxide, or Alumina, or A combination of both oxides, It consists of: Optionally, Carbon nanotubes, Graphene, Fullerene, yttrium oxide, Cerium oxide, Zirconium carbide, Silicon carbide, Titanium carbide, zirconium boride, Boron nitride, Titanium nitride, and Silicon nitride The axis of claim 1 , further comprising one or more elements of:

3. The ceramic is mainly made of silicon nitride, Optional Carbon nanotubes, Graphene, Fullerene, Zirconium oxide, Aluminum oxide, yttrium oxide, Cerium oxide, Zirconium carbide, Silicon carbide, Titanium carbide, zirconium boride, Boron nitride, and Titanium nitride The axis of claim 1 , further comprising one or more elements of:

4. The shaft according to claim 1 , wherein the first part has a surface of revolution, in particular a cylindrical or conical or frusto-conical or curve-generating surface.

5. The shaft according to any one of claims 1 to 4, wherein the shaft or the first functional part has a convex (212') or concave (212") or conical (212*) or frusto-conical end.

6. The second functional part (3), in particular a second functional part (31, 32, 33; 34; 35; 45) for receiving a timepiece part, in particular a balance, a plate, a collet, a wheel, another axle (6), an ébauche (81), or a second pivot part for the timepiece part on said shaft, or The second occlusal portion, in particular the teeth, The shaft according to claim 1 , comprising:

7. The shaft according to claim 6, wherein the second functional portion has a second outer diameter (D2) less than 2 mm, or less than 1 mm, or less than 0.5 mm.

8. 8. The shaft of claim 7, wherein the ratio of the first diametric dimension to the second diametric dimension is less than 0.9, or less than 0.8, or less than 0.6, or less than 0.5, or less than 0.

4.

9. A shaft as claimed in any one of claims 1 to 8, wherein the shaft is made entirely of ceramic.

10. An assembly (41; 42) comprising a shaft (1) according to any one of claims 1 to 9 and at least one guide (51; 52; 53), in particular a bearing (51; 52) or a groove (53), The axis is Rotating or pivoting within said at least one guide; and / or translating within said at least one guide; An assembly that is designed to:

11. said at least one guide (51) comprises a bearing stone (511) and a jewel (512) which cooperate with said pivot or pivot body to guide said shaft in said guide; Assembly (41) according to claim 10.

12. 11. An assembly (42) as claimed in claim 10, wherein said at least one guide (52) comprises a ball track (521) and a ball (522), said ball cooperating by contact with said pivot (21*) to guide said shaft into said guide.

13. A spring-balance type oscillator (100) having an axis (1; 1') according to any one of claims 1 to 9 and / or an assembly according to any one of claims 10 to 12.

14. A miniature clock movement (110) comprising an oscillator (100) according to claim 13 and / or an assembly according to any one of claims 10 to 12 and / or an axle (1; 1'; 1") according to any one of claims 1 to 9.

15. A timepiece (120) comprising a miniature timepiece movement (110) according to claim 14 and / or an oscillator (100) according to claim 13 and / or an assembly according to any one of claims 10 to 12 and / or an axle (1; 1'; 1") according to any one of claims 1 to 9.

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