Classifications

• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B17/00—Mechanisms for stabilising frequency
  • G04B17/04—Oscillators acting by spring tension
  • G04B17/06—Oscillators with hairsprings, e.g. balance
  • G04B17/066—Manufacture of the spiral spring
• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B17/00—Mechanisms for stabilising frequency
  • G04B17/04—Oscillators acting by spring tension
  • G04B17/045—Oscillators acting by spring tension with oscillating blade springs

Definitions

• a watch resonator generally consists of a balance and a hairspring mounted on the axis of the balance and serving as a return spring to the balance.
• the oscillations of the balance wheel are maintained by an escapement.
• the resonator and the exhaust together form an oscillator.
• the pendulums generally oscillate between amplitudes of 240 and 300°. In this range, the average rate of the hairspring (average of the steps in its different horizontal and vertical positions) is decreasing so that it can compensate for the delay due to the escapement, as described in patent EP 2917787 of the present applicant and mentioned in patent EP 2299336 in the name of Rolex SA.
• the present invention aims to remedy this drawback and to this end proposes a hairspring according to claim 1.
• variations in rigidity and/or pitch are generally used to make the development of the hairspring concentric, cf. . for example patent EP 1473604 of the present applicant and the aforementioned patent EP 2299336 on behalf of Rolex SA.
• these variable rigidities and/or steps do not change, or only very little, the shape of the walking curves for small amplitudes.
• - Figure 1 is an isochronism diagram (step), obtained by analytical modeling, of a traditional hairspring in the shape of Archimedes' spiral positioned horizontally;
• - Figures 2 and 3 are reproductions of Figures 4 and 8 of patent EP 2299336, which represent isochronism curves of hairsprings whose thickness and pitch vary in a non-monotonic manner to make the development of the hairspring substantially concentric;
• - Figure 4 is a plan view of a hairspring according to a first embodiment of the invention; the numbers 3, 6, 9 and 12 around the hairspring indicate the angular position of the hairspring relative to the dial of the timepiece that it is intended to equip;
• - Figure 5 is a diagram of the thickness of the blade of the hairspring of Figure 4 as a function of the number of turns measured from the inner end of the hairspring;
• - Figure 6 is a diagram of the pitch of the hairspring of Figure 4 as a function of the number of turns measured from
• Figure 1 shows the theoretical isochronism curve of a traditional hairspring in the shape of an Archimedean spiral and with constant blade thickness, in a horizontal position.
• the aforementioned isochronism curve is the rate curve due to the eccentric development of the balance spring in the horizontal position, that is to say the rate curve due to the reactions of the pivots of the balance axis to the decentering of the balance spring.
• step ⁇ 1 is identical in all positions, horizontal and vertical, of the oscillator. The same applies to the movement due to the exhaust.
• rate ⁇ 2 due to the weight of the hairspring differs depending on the vertical position.
• the average of the steps ⁇ 2 for the four vertical reference positions (3H, 6H, 9H and 12H) spaced 90° apart is zero.
• FIGS 2 and 3 are reproductions of Figures 4 and 8 of patent EP 2299336.
• the curve FH of each of these figures corresponds to the step ⁇ 1 described above, namely to the step due to the eccentric development of the balance spring in the horizontal position or walking due to the reactions of the pivots. If we draw the average curve of the steps in the four vertical positions (average of the 3H, 6H, 9H and 12H curves), we see that it is confused with the FH curve, which is consistent with the point above .
• the CH curve in each of Figures 2 and 3 does not only represent the movement due to the reactions of the pivots.
• the hairsprings according to patent EP 2299336 are formed of a blade of variable thickness (more generally of variable rigidity) wound at a pitch which also varies.
• the variations in thickness and pitch are chosen so that the development of the hairspring is substantially concentric and thus the radial forces of the pivots in their bearings are substantially zero.
• the FH curve shows that the step due to the reactions of the pivots only decreases from an amplitude of approximately 200° (figure 2) or does not decrease (figure 3), which makes it impossible to compensate for the step delay. due to exhaust for small amplitudes.
• the hairspring is designed with a variable blade thickness and/or a variable pitch so as to obtain a decreasing rate ⁇ 1 in a range of amplitudes including small amplitudes.
• the thickness of the hairspring blade and the pitch of the hairspring are measured radially with respect to the geometric center of the hairspring.
• the pitch that is to say the distance between two consecutive turns, is measured between the neutral fibers of the turns. Examples of hairsprings according to the invention are illustrated in Figures 4, 9 and 14.
• These hairsprings are made of a silicon-based material, more precisely of silicon covered with a thermal compensation layer of silicon oxide, and have a height of turns of 120 ⁇ m, a distance between their inner end and their geometric center (distance measured between the neutral fiber and the geometric center) of 0.565 mm, a distance between their outer end and their geometric center (distance measured between the neutral fiber and the geometric center) of 2.35 mm and a number of turns which varies from one hairspring to another, i.e. respectively 9.62 turns, 8.44 turns and 7.37 turns for the hairsprings in Figures 4, 9 and 14.
• the thickness of the blade forming the hairspring decreases continuously and over more than one revolution from the inner end of the hairspring (abscissa 0 on the diagram) until reaching a minimum. Then, from this minimum, the thickness of the blade increases continuously and over more than one revolution until the outer end of the hairspring.
• the pitch of these examples of hairsprings is illustrated in Figures 6, 11 and 16. It grows continuously over more than half its length, in number of turns, and can grow continuously from the inner end to the outer end.
• the thickness of the blade forming the hairspring to decrease continuously and over more than one turn in the direction of winding of the blade from a first point located on the inner turn and decreases continuously and over more than one turn in the direction opposite to the direction of winding of the blade from a second point located upstream of the first point in said direction opposite to the direction of winding of the blade.
• the second point is located on the outer turn or on the turn which immediately follows the outer turn in said direction opposite to the direction of winding of the blade.
• the first point may be the inner end of the hairspring or a point distinct from the inner end.
• the second point may be the outer end of the hairspring or a point distinct from the outer end.
• the thickness of the blade decreases continuously from the first point until reaching a minimum (which can be the thickness of a single point of the hairspring or 'a portion of the hairspring), then grows continuously from this minimum to the second point.
• a minimum which can be the thickness of a single point of the hairspring or 'a portion of the hairspring
• the thickness at the first point is greater, and even greater by a factor greater than 2, than the thickness at the second point.
• Figures 7, 12 and 17 show the step ⁇ 1 due to the eccentric development of the hairspring in the horizontal position for the hairsprings of Figures 4, 9 and 14 respectively.
• the rate ⁇ 1 is decreasing, which makes it possible to compensate for the increasing rate of an escapement, in particular of an escapement with a Swiss lever.
• the balance springs in Figures 4, 9 and 14 produce a rate difference ⁇ 1 between the amplitudes of 130° and 220° greater than 1.2 s/d, 1.5 s/d and 5 s/d respectively, allowing to compensate for a corresponding delay in operation due to exhaust in this amplitude range.
• the balance springs according to the invention preferably produce a rate difference ⁇ 1 between the amplitudes of 130° and 220° of at least 1 s/d, or even at least 1.5 s/d, or even at least 2 s/d, or even at least 3 s/d, or even at least 4 s/d.
• These examples of hairsprings are also designed such that the minimum distance between the turns, at the most unfavorable location in contraction, distance measured between the two facing faces, is 25 ⁇ m.
• Figures 8 and 13 show the step ⁇ 2 due to the weight of the hairspring for the hairsprings of Figures 4 and 9 respectively.
• the rate ⁇ 2 is shown for the four vertical reference positions 3H, 6H, 9H and 12H spaced at 90°.
• the step ⁇ 2 is canceled at an oscillation amplitude between 200° and 240°, or even between 210° and 230°.
• This passage of the curves through zero at approximately 220°, rather than at amplitudes of 163.5° and 330.5° as in the case of an Archimedes spiral makes it possible to apply the teachings of patent EP 3433680 and patent application EP 3913441 of the present applicant, that is to say in particular to compensate for the step ⁇ 2 due to the weight of the balance spring by the step due to the lack of balance of the balance, the lack of balance of the balance (unbalance and angular position of the center of gravity) being chosen for this purpose. In this way, the walking differences between the different vertical positions are minimized.
• the present invention is therefore possible in the present invention to optimize both the isochronism of the oscillator, by making variations in the rate or frequency as a function of the oscillation amplitude, and the steps at the positions minimal. , and this while the hairsprings have an eccentric, even very eccentric, development.
• the present invention is not limited to the examples of hairsprings described above. Other combinations of thickness and pitch variations can be found. It is also possible to vary only the thickness or the pitch. Furthermore, an alternative to varying the thickness would be to vary the rigidity of the blade in another way, for example by heat treatment or silicon doping.
• the present invention is also not limited to silicon. Other materials, in particular metallic, can be used.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Springs (AREA)
• Micromachines (AREA)

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• 2022
  • 2022-06-14 EP EP22178975.3A patent/EP4293428A1/de not_active Withdrawn
• 2023
  • 2023-06-14 WO PCT/IB2023/056135 patent/WO2023242756A1/fr not_active Ceased
  • 2023-06-14 WO PCT/IB2023/056116 patent/WO2023242746A1/fr not_active Ceased
  • 2023-06-14 EP EP23735864.3A patent/EP4540665A1/de active Pending
  • 2023-06-14 EP EP23735869.2A patent/EP4540666A1/de active Pending

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