CH716332B1 - Clockwork shaft with structured pivot. - Google Patents

Abstract

The invention relates to a clockwork shaft (1) for the rotational mounting of at least one member comprising a bearing surface (22) intended to receive the member and a pivot (21) at each of its two free ends intended to pivot in a bearing to make the member rotatable. According to the invention, at least one of the two pivots (21) comprises a structuring (25) of its external surface in order to minimize its contact surface with the bearing.

Description

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a clock shaft of which at least one of the pivots is improved in order to improve its tribology in a bearing.

TECHNICAL BACKGROUND OF THE INVENTION

[0002] It is constantly sought to minimize the coefficients of friction in watch movements. In the case of clock shafts, the aim is thus to achieve the lowest possible loss of mechanical energy due to friction.

SUMMARY OF THE INVENTION

The invention aims to provide a clock shaft whose tribology in a bearing is improved to reduce mechanical energy losses.

[0004] To this end, the invention relates to a clock shaft for the rotational mounting of at least one member comprising a bearing surface intended to receive the member and a pivot at each of its two free ends intended to pivot in a bearing to make the member rotatable, characterized in that at least one of the two pivots comprises a structuring of its external surface in order to minimize its contact surface with the bearing.

[0005] Advantageously according to the invention, the contact surface of the clock shaft with the bearing, such as the wall of the hole of a bearing, can therefore be modified in order to adjust the associated mechanical energy losses. In combination with a lubricant, it is also desired that the structuring provide a lift effect of the lubricant and recirculation of the lubricant on the surface of the pivot. It is therefore understood that the structuring advantageously makes it possible to reduce the coefficient of friction and the wear of the pivot against the bearing.

[0006] The invention may also comprise one or more of the following optional characteristics, taken alone or in combination.

[0007] The structuring may comprise at least one pattern having a width, a length and a recessed depth in the outer surface of the pivot in order to selectively modify the contact surface of the clock shaft with the bearing. A capillarity effect is also sought to retain any lubricant at the level of the pivot thanks to the structuring.

[0008] The recessed pattern of the structuring may comprise a width L comprised between 300 nm and 1 μm. In addition, the recessed pattern may comprise a ratio between the width and the depth comprised between 5 and 20.

[0009] The structuring can, for example, represent between 5% and 50% of the outer surface of the pivot and, preferably, 30% in order to reduce the contact surface of the clock shaft with the bearing.

[0010] The structuring can form at least one groove in order to form a circulation channel for a lubricant on the outer surface of the pivot and/or at least one recess in order to form a reservoir for a lubricant on the outer surface of the pivot.

[0011] The shaft may comprise conical pivot ends, a cylindrical base of at least one of the two pivots, called contact surface, comprising a structuring of its external surface in order to selectively differentiate the coefficient of friction of the surface of contact relative to that of the tapered end of the shaft pivot. This particular example applied to a balance shaft advantageously makes it possible to minimize the differences in amplitude of the balance between the horizontal and vertical positions.

Finally, the invention relates to a watch movement comprising at least one bridge and one plate each provided with bearings and at least one watch shaft assembled between a bearing of the bridge and a bearing of the plate in order to be pivotally mounted , characterized in that the clock shaft is as presented above. By way of no limitation, the clock arbor may be a balance shaft, an anchor rod, a toothed wheel arbor and/or a barrel arbor.

BRIEF DESCRIPTION OF DRAWINGS

Other features and advantages of the invention will emerge clearly from the description which is given below, by way of indication and in no way limiting, with reference to the appended drawings, in which: Figure 1 is a schematic view of a timepiece according to the invention; FIG. 2 is a perspective view of a clock shaft with a structure according to the invention; FIGS. 3a to 3c are schematic structural views of a pivot according to a first embodiment of the invention; FIGS. 4a to 4c and 5a to 5d are schematic structural views of a pivot according to a second embodiment of the invention; FIGS. 6a to 6d are schematic structural views of a pivot according to the first and second combined embodiments of the invention; Figure 7 is a partial schematic sectional view of a shaft assembled in a bearing; FIG. 8 is a partial schematic view of an escapement mechanism of a watch movement. ; Figure 9 is a partial schematic view of a resonator of a watch movement.

DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT OF THE INVENTION

In the various figures, identical or similar elements bear the same references, possibly with the addition of an index. The description of their structure and function is therefore not systematically repeated.

[0015] In what follows, the orientations are the orientations of the figures. In particular, the terms „upper“, „lower“, „left“, „right“, „above“, „below“, „forward“ and „backward“ generally mean with respect to the direction of representation of the figures.

[0016] By "timepiece 2" is meant all types of instruments for measuring or counting time such as clocks, clocks and watches.

[0017] By “watchmaking movement 3”, we mean all types of mechanism capable of counting time, whether they are powered by mechanical energy (for example a barrel) or electricity (for example a battery).

The invention relates to a shaft 1 for a watch movement 3 intended to equip a timepiece 2 as illustrated in Figure 1. An example of watch movement 3 is partially shown in Figure 7. It can thus comprise at least one bridge 5 and one plate 6 each provided with bearings 7. It also comprises at least one clock shaft 1 assembled between a bearing 7 of the bridge 5 and a bearing 7 of the plate 6 (only one end is illustrated in FIG. 7 for simplification) in order to be pivotally mounted between the bridge 5 and the plate 6.

A bearing 7 generally comprises a body 8 in which is mounted a bearing 9 whose hole 10 receives the pivot 21 of the shaft 1. In the example of Figure 7, the bearing 7 further comprises a kitten 12 elastically mounted flat in the body 8 of the bearing 7 such as, for example, using a spring (not shown) sometimes called a lyre. The kitten 12 supports the bearing 9 and a counter-pivot 11 and can by its elastic assembly absorb the shocks received by the pivots 21 of the shaft 1. Such an arrangement is generally called a bumper bearing or parachute bearing. The bearing 9 and the counter-pivot 11 are generally based on ruby and, as such, can sometimes be called respectively stone 9 and counter-pivot stone 11. Of course, other types of bearings can be provided such as a crapaudine but also other types of materials than ruby. The bearing 7 could thus be wholly or partly formed from a ceramic and/or a carbon-based material.

[0020] In no way limiting in the examples of Figures 8 and 9, the shaft 1 watchmaker can thus form a balance axis A 13, an anchor rod B 17, a toothed wheel shaft C 18 and / or a barrel arbor (not shown) of a watch movement 3. An example of a watchmaker's shaft 1 is represented in FIG. 2. As explained above, the watchmaker's shaft 1 can be used for the rotational mounting of at least one member such as a balance wheel 13, a hairspring 14, a large plate 15, a small plate 16, an anchor 17, a toothed wheel 18, a pinion 19 and/or a barrel spring (not shown) of a watch movement 3.

[0021] The watchmaker's shaft 1 can thus comprise a bearing surface, also called seat 22, intended to receive the member, rods 23, a rod 24 and a pivot 21 at each of its two free ends intended to pivot in a bearing 7 to make the member rotatable. Such a shaft 1 is generally formed from steel such as, for example, type 20AP.

[0022]Of course, other shaft geometries can be provided depending on the application and the number of members to be received. The bearing surface 22 intended to receive the member could thus be formed by another part of the shaft 1. Thus, in no way limiting, the bearing surface could not be a seat 22 but by one of the rods 23. In addition, d other types of materials than steel can be considered. The shaft 1 could thus be wholly or partly formed from a ceramic and/or a carbon-based material (DLC or diamond) and/or any other material that is not very sensitive to magnetic fields, such as molybdenum disulphide (MoS2) for example. or tungsten disulfide (WS2).

According to the invention, at least one of the two pivots 21 comprises a structuring 25 of its external surface 26 in order to minimize its contact surface with the bearing 7 and, more particularly the wall of the hole 10 of the bearing 9. Advantageously according to the invention, the contact surface of the clock shaft 1 with the bearing 7, such as the wall of the hole 10 of a bearing 9, can therefore be modified in order to adjust the associated mechanical energy losses. A capillarity effect is also sought to retain the oil or the lubricant at the level of the pivot 21 thanks to the structuring 25.

The structuring 25 may include at least one recessed pattern 27 on the outer surface 26 of the pivot 21 in order to selectively modify the contact surface of the watch shaft 1 with the bearing 7. The pattern 27 extends over a angular sector of the pivot 21 and thus forms an imprint having a width L, a depth and a length. It should thus be understood that from a usual shaft 1 with a conical pivot 21 that the structuring 25 can be obtained in a destructive manner, that is to say by selectively hollowing out the material of the pivot 21 (laser radiation, attack chemical, etc.), or in an additive way, that is to say by selectively depositing a material on the pivot 21 (electrolytic deposition, physical vapor deposition, etc.), in order to form each pattern 27 in hollow to the outer surface 26 of the pivot 21.

[0025] Whether as an overlay or in the material of the shaft 1, the structuring 25 preferably represents between 5% and 50% of the outer surface 5 of the pivot 21 and, preferably, 30% in order to reduce the surface of contact between shaft 1 of the watchmaker and bearing 7.

The recessed pattern 27 of the structuring 25 can form at least one groove 27a in order to form a circulation channel for a lubricant on the outer surface 26 of the pivot 21 and/or at least one recess 27b in order to form a reservoir for a lubricant on the outer surface 26 of the pivot 21. Indeed, the bearings 7 are generally lubricated in particular with the aid of an oiler 20 at the level of the bearing 9. Thus, the structuring 25 also makes it possible to maintain a more uniform film of lubricant to the outer surface 26 of the pivot 21.

According to a first embodiment, the pivot 21 comprises a structuring 25 formed solely on the basis of at least one recess 27a in order to form reservoirs distributed homogeneously or not on the outer surface 26 of the pivot 21. As in no way limiting, FIGS. 3a to 3c are examples of the first embodiment according to the invention. In the first variant illustrated in Figure 3a, the pivot 21 comprises a structure 25 formed of recesses 27a of substantially rectangular sections distributed all around the outer surface 26. Each recess 27a is oriented substantially parallel with respect to the length of the shaft 1. In the second variant illustrated in FIG. 3b, the pivot 21 comprises a structure 25 formed of recesses 27a of substantially circular sections distributed all around the surface 26 external. Finally, in a third variant illustrated in FIG. 3c, the pivot 21 comprises a structure 25 formed by recesses 27a of substantially rectangular sections distributed all around the outer surface 26 . Each recess 27a is oriented substantially perpendicular to the length of the shaft 1.

Of course, the variants of the first embodiment can be combined and/or each recess 27a can have a different geometry to the others and/or the recesses 27a can be distributed differently (different density for the same surface, different distribution in particular asymmetrical, etc.) on the outer surface 26 of the pivot 21.

According to a second embodiment, the pivot 21 comprises a structure 25 formed solely on the basis of at least one groove 27b in order to form circulation channels distributed homogeneously or not on the outer surface 26 of the pivot 21. By way of no limitation, FIGS. 4a to 4c and 5a to 5d are examples of the second embodiment according to the invention. In the first variant illustrated in FIG. 4a, the pivot 21 comprises a structure 25 formed by a substantially helical groove 27b on the external surface 26 . In the second variant illustrated in Figure 4b, the pivot 21 comprises a structure 25 formed of a substantially helical groove 27b and substantially vertical grooves 27b crossing the substantially helical groove 27b on the outer surface 26. In a third variant illustrated in FIG. 4c, the pivot 21 comprises a structure 25 formed of a first substantially helical groove 27b and a second substantially helical groove 27b crossing the first substantially helical groove 27b and winding in the opposite manner to the first substantially helical groove 27b on the outer surface 26.

In the fourth variant illustrated in Figure 5a, the pivot 21 comprises a structure 25 formed of grooves 27b zigzag around the outer surface 26. In the fifth variant illustrated in FIG. 5b, the pivot 21 comprises a structure 25 formed of zigzag grooves 27b extending substantially vertically on the outer surface 26. In a sixth variant illustrated in Figure 5c, the pivot 21 comprises a structure 25 formed of a first series of grooves 27b in zigzag around the outer surface 26 and a second series of grooves 27b in zigzag around the surface 26 external intersecting the first series of zigzag grooves 27b around the outer surface 26 and extending offset or out of phase with respect to the first series of zigzag grooves 27b around the outer surface 26. In a seventh variant illustrated in Figure 5d, the pivot 21 comprises a structure 25 formed of a first series of zigzag grooves 27b extending substantially vertically on the outer surface 26 and a second series of zigzag grooves 27b s extending substantially vertically on the outer surface 26 intersecting the first series of zigzag grooves 27b extending substantially vertically on the outer surface 26 and extending offset or out of phase with respect to the first series of zigzag grooves 27b extending substantially vertically over the outer surface 26.

Of course, the variants of the second embodiment can be combined and/or each groove 27b can have a different geometry to the others and/or the grooves 27b can be distributed differently (different density for the same surface, different distribution in particular asymmetrical, etc.) on the outer surface 26 of the pivot 21.

According to a third embodiment, the pivot 21 comprises a structure 25 formed based on at least one recess 27a in order to form reservoirs distributed homogeneously or not on the outer surface 26 of the pivot 21 and based on at least one groove 27b in order to form circulation channels distributed homogeneously or not on the outer surface 26 of the pivot 21. By way of no limitation, FIGS. 6a to 6d are examples of the third embodiment according to the invention .

In the first variant illustrated in Figure 6a, the pivot 21 comprises a structure 25 formed of a first series of zigzag grooves 27b around the outer surface 26, a second series of zigzag grooves 27b around the outer surface 26 crossing the first series of zigzag grooves 27b around the outer surface 26 and extending offset or out of phase with the first series of zigzag grooves 27b around the outer surface 26, and recesses 27a of substantially circular sections distributed between two pairs of first and second series of zigzag grooves 27b crossed all around the outer surface 26.

In the second variant illustrated in Figure 6b, the pivot 21 comprises a structure 25 formed of zigzag grooves 27b around the outer surface 26 and recesses 27a of substantially rectangular sections (extending substantially parallel to the length of the shaft 1) distributed between two zigzag grooves 27b all around the outer surface 26.

In a third variant illustrated in Figure 6c, the pivot 21 comprises a structure 25 formed of a substantially helical groove 27b on the outer surface 26, first recesses 27a of substantially rectangular sections (extending substantially perpendicular to to the length of the shaft 1) distributed around the turns of the groove 27b all around the outer surface 26 and second recesses 27a of substantially rectangular sections (extending substantially parallel to the length of the shaft 1) distributed between a turn of the groove 27b and a first recess 27b in order to make them communicate together.

In the fourth variant illustrated in Figure 6d, the pivot 21 comprises a structure 25 formed of a substantially helical groove 27b on the outer surface 26 and recesses 27a of substantially circular sections distributed around the turns of the groove 27b all around the outer surface 26.

Of course, the variants of the third embodiment can be combined and/or each recess 27a can have a different geometry to the others and/or the recesses 27a can be distributed differently (different density for the same surface, different distribution in particular asymmetrical, etc.) on the outer surface 26 of the pivot 21 and/or each groove 27b can have a different geometry to the others and/or the grooves 27b can be distributed differently (different density for the same surface, different distribution, in particular asymmetrical , etc.) on the outer surface 26 of the pivot 21.

Whatever the embodiment or the variant of the invention, the maximum dimension of the contour of the pattern 27 on the surface of the pivot 21 measured in a plane perpendicular to the axis of the pivot 21, that is to to say substantially the width L, is preferably between 300 nm and 1 μm, that is to say, for example, 300 nm, 350 nm, 400 nm, 450 nm, 475 nm, 500 nm, 525 nm, 550 nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm. In addition, the structuring 25 can include a ratio between the width L and the depth of between 5 and 20, that is to say if the width L of the structuring is equal to 500 nm, the depth of the structuring 25 is preferably between 100 nm and 25 nm. Of course, the dimensions of the width L, the depth and the length of the patterns 27 can be different from these preferred dimensions without departing from the scope of the invention. In no way limiting, the width L could thus be greater than 1 μm without departing from the scope of the invention.

Of course, each embodiment and/or variant may have a percentage coverage of the pivot 21 and/or a structuring density 25 and/or a pattern width L 27 and/or a pattern depth 27 of its own ( s) with respect to other embodiments and/or variants. It can also be envisaged that the percentage of coverage of the pivot 21 and/or the density of structuring 25 and/or the width L and/or the depth of the structuring 25 evolve(s) on the external surface 26 of the pivot 21, by example, depending on the location on the pivot 21. In no way limiting, it could be envisaged that the structuring 25 decreases in density and/or in width L and/or in depth as the outer surface 26 of the pivot 21 moves away from the oiler 20 of the bearing 9, that is to say both towards the rod 23 and towards the free end of the pivot 21.

[0040] In the particular example of an axis A of balance wheel 13, the invention could bring an additional advantage. Indeed, it is constantly sought to minimize the amplitude differences of the balance 13 (maximum angle of the balance 13 at each alternation) between the horizontal (HH, HB) and vertical (VH, VG, VD, VB) positions of the part 2 clocks. Typically, it is generally desired that the friction moments at the two positions (HH, HB, VH, VG, VD, VB) be identical.

The flat friction moment is written:

[0042] The hangman friction moment is written: Mpendu= µpenduPr (2)

[0043] Where: µ is the coefficient of friction of the position; P is the weight of the oscillator; r1 is the outer radius of the flat friction surface; r0 is the inner radius of the flat friction surface; r is the radius of the axis in contact with the hangman bearing.

[0044] To minimize the differences, it is sought to obtain: Mplat= Mpendu. (3)

This results in the following equality:

If either a 33% lower coefficient of friction when hanged, then the moment of friction when hanged will be substantially equivalent to the moment of friction when flat. The solution usually implemented is to make flats on the ends of pivots 21 to minimize the amplitudes in horizontal positions, that is to say that the horizontal amplitudes are degraded to bring them closer to the vertical amplitude values.

Advantageously according to the invention, at least one of the two pivots 21 of the axis A of the balance 13 comprises a structuring 25 of its outer surface 26 at the level of the cylindrical base of the pivot 21 which comes into contact with the hole 10 of the pad 9 in order to minimize friction when hanging to increase the amplitudes in at least one of the vertical positions. Conversely to the solution usually implemented, the structuring 25 according to the invention makes it possible to keep a conical free end of the pivot 21 and therefore offers a gain in coefficient of friction allowing the moment of friction at the hangman to be substantially equivalent to the moment of flat friction without having to degrade the horizontal amplitudes. It is therefore understood that the amplitudes will be identical between the positions (difference between flat and hanging low or zero as previously) but with a greater chronometric performance in particular by the higher amplitudes obtained whatever the positions.

Claims (9)

1. Watchmaker shaft (1) for the rotational mounting of at least one member comprising a bearing surface (22) intended to receive the member and a pivot (21) at each of its two free ends intended to pivot in a bearing ( 7) to make the member rotatable, characterized in that at least one of the two pivots (21) comprises a structuring (25) of its outer surface (26) in order to minimize its contact surface with the bearing (7 ). 2. Shaft (1) watchmaker according to the preceding claim, wherein the structuring (25) comprises at least one pattern (27, 27a, 27b) having a width (L), a length and a recessed depth on the surface (26 ) external of the pivot (21). 3. Shaft (1) watchmaker according to the preceding claim, wherein the pattern (27, 27a, 27b) in hollow of the structuring (25) has a width (L) of between 300 nm and 1 micron. 4. Tree (1) watchmaker according to claim 2 or 3, wherein the pattern (27, 27a, 27b) recessed in the structuring (25) has a ratio between the width (L) and the maximum depth of between 5 and 20. 5. Shaft (1) watchmaker according to one of the preceding claims, wherein the structuring (25) represents between 5% and 50% of the outer surface (26) of the pivot (21). 6. Shaft (1) watchmaker according to one of the preceding claims, wherein the structuring (25) forms at least one groove (27b) to form a circulation channel for a lubricant on the outer surface (26) of the pivot ( 21). 7. Shaft (1) watchmaker according to one of the preceding claims, comprising conical pivot ends (21), a cylindrical base of at least one of the two pivots (21), called contact surface, comprising a structuring (25 ) of its outer surface (26) in order to selectively differentiate the coefficient of friction of the contact surface with respect to that of the conical end of the pivot (21) of the shaft (1). 8. Watchmaking movement (3) comprising at least one bridge (5) and one plate (6) each provided with bearings (7) and at least one watchmaking shaft (1) assembled between a bearing (7) of the bridge (5) and a bearing (7) of the plate (6) in order to be pivotally mounted, characterized in that the said at least one horological shaft (1) is according to one of claims 1 to 7. 9. Watchmaking movement (3) according to the preceding claim, wherein said at least one watchmaking shaft (1) is a balance shaft (A) (13), an anchor rod (B) (17), a shaft ( C) of a toothed wheel (18) or a barrel shaft.