EP2788825A1

EP2788825A1 - Method for adjusting the chronometry of a timepiece movement intended to operate in a low-pressure atmosphere

Info

Publication number: EP2788825A1
Application number: EP12812337.9A
Authority: EP
Inventors: Kéwin Bas; Cyrille Chatel
Original assignee: Cartier Creation Studio SA
Current assignee: Cartier International AG
Priority date: 2011-12-09
Filing date: 2012-11-30
Publication date: 2014-10-15
Also published as: US20150192900A1; JP2015500479A; US9389588B2; CN103975282B; WO2013084040A1; CN103975282A

Abstract

The invention relates to a method for adjusting the chronometry of a mechanical timepiece movement intended to operate in a low-pressure atmosphere, comprising the following successive operations: 1. placing the movement in an atmosphere at the low-pressure pre-established for the normal operation of the movement; 2. measuring the advance or delay (typically advance +ΔΡ) of the timekeeping precision of the movement at said low pressure. 3. returning the movement to ambient atmospheric pressure; 4. adjusting the movement in order to compensate for the advance or delay previously measured (typically implementing a delay -ΔΡ) during operation at low pressure; 5. returning the movement to the atmosphere at the low pressure pre-established for the normal operation of the movement.

Description

Method for adjusting the chronometry of a watch movement intended to operate in a low-pressure atmosphere

The present invention relates to the adjustment of the chronometry of a mechanical clockwork movement intended to operate in a low-pressure atmosphere, that is to say, fitted in a sealed box in which the pressure has been lowered below the atmospheric pressure and possibly modified the composition of the atmosphere to limit the oxidation, wear and aging of certain elements of the movement. By "vacuum" or "protected atmosphere" or "low pressure atmosphere" here is meant a generally low pressure with respect to atmospheric pressure, with or without an added gas that is kept inside a box that has been optimized to keep this low pressure.

Documents such as CH 15501, CH 556564, CH 355742, CH 336765, CH 463402 or GB 1272 83 relating to watches intended to operate under a reduced-pressure atmosphere are known. These documents recommend the use of a reduced operating pressure to either reduce the oxidation of metals and lubricants or improve the sealing of the watch case.

In document FR2054540, it is furthermore found that by reducing the pressure prevailing inside a watch case, the energy loss due to the friction of the air tends towards zero and therefore the Oscillator quality of the watch movement increases considerably.

In order to improve the chronometric qualities of a watch movement, the document FR2054540 proposes three variants of a timepiece comprising an oscillator working in an enclosure in which there is a reduced pressure of between 10 ^"1 - 10 ^{" 5} mm Hg (0.13 mbar - 1.3.10 ^"5 mbar) According to the first and second variants, the low pressure prevails everywhere inside the watch case and the oscillator comprises a balance-spiral, a racket able to modify the frequency and two bimetallic blades. to act on the racket and to increase or decrease the frequency of the oscillator when either one of these bimetallic strips is heated by an electric wire controlled by the outside of the box. According to the third variant, the oscillator is a spiral balance held electronically by coils cooperating with a magnetic field created by two magnets. In this third variant, only the oscillator and its maintenance and adjustment means are contained in a hermetically sealed enclosure. As in the other variants, bimetals inside the enclosure act on the racket by a thermal effect controlled by means outside the enclosure.

Although a movement according to FR2054540 is designed according to the high vacuum in which its oscillator operates, the latter requires the presence and operation of very complicated adjustment means and of uncertain accuracy and reliability. The presence of magnetic elements within a watch movement is also problematic because it can lead to

15 harmful effects on the movement's progress.

Similarly, FR1546744 discloses a precision timepiece apparatus in which a low pressure atmosphere of one hundredth of Torr (0.013 mbar) is established inside a carrier box. According to one variant, the box comprises a valve and the movement is provided with a racket allowing regulation by electromagnetic influence through the box.

In this case, after the casing movement, the pressure inside the box is reduced through the valve, and subsequently the oscillator is adjusted by electromagnetic means. This variant has the same disadvantages as a movement according to FR2054540 above. According to a second variant suggested in FR1546744, the box has no valve, and once it is provided with its movement, it is directed towards a vacuum chamber, where the movement is set under vacuum by chronographs. comparators by directly attacking the tuning racket as for a conventional tuning under atmosphere. After this adjustment and always under vacuum, the bowl is screwed with seal, and the watch leaves the vacuum chamber.

This variant, which also corresponds to the usual processes for adjusting a movement intended to operate under a reduced pressure atmosphere, completely ignores the major difficulties presented by the need to operate the racket directly when the watch is inside the rack. a vacuum chamber, and the document FR1546744 offers no solution for this major challenge. Indeed, the watch must be open in the vacuum chamber to allow adjustment of the racket using complicated means to work in the vacuum chamber, then the watch must be closed tightly before being released of the vacuum chamber.

These documents of the prior art clearly show that it is necessary, for a watch operating under a reduced pressure atmosphere, to adjust the frequency of its oscillator while the watch or at least part of its movement is maintained in a low pressure chamber which involves complex adjustment means, namely the opening and closing of the watch case in a vacuum chamber equipped with means for adjusting the oscillator by tools located in the vacuum chamber or to provide means capable of adjusting the oscillator from outside the box.

In fact in the prior art found, only the documents FR 1546744 and FR

2054540 are concerned with the tuning of the oscillator operating at low pressure and these documents involve an adjustment of the regulating member when the movement is subjected to the low expected operating pressure, which is a complicated task requiring special means for the adjustment .

The object of the present invention is to provide a method for the chronometric adjustment of the oscillator of a mechanical clockwork movement intended to operate in a low-pressure atmosphere when the movement is subjected to ambient atmospheric pressure. This overcomes the disadvantages of the known devices since it is no longer necessary to provide special means for the time adjustment of the movement under reduced pressure atmosphere, this adjustment is performed only at atmospheric pressure.

The invention applies mainly to a mechanical clockwork movement comprising at least one oscillator or regulating member in the form of a balance-spring. This mechanical watchmaking movement generally still comprises at least one barrel, an escapement maintaining the oscillations of the sprung balance and a finishing train transmitting the driving force of the barrel to the exhaust. This chronometric adjustment method applies more particularly to a line or set of movements of the same caliber comprising equivalent or identical assortments.

The aim to be achieved is obviously that the mechanical clockwork movement has, when operating in the atmosphere at a reduced pressure to a predetermined value, preferably between 5 mbar and 0.1 mbar, a chronometric accuracy of substantially zero second per day subject to generally accepted standard variation tolerances.

The method according to the invention comprises the following steps:

1. put the motion into atmosphere at the pre-set low pressure for normal movement operation,

2. measure the advance or recoil (+ ΔΡ) of the chronometric accuracy of the movement at this low pressure, 3. restore the movement to ambient atmospheric pressure,

4. adjust the movement subjected to the ambient atmospheric pressure to compensate for the advance or the recoil measured previously (by -ΔΡ) during low pressure operation, 5. Return the movement to atmosphere at the pre-set low pressure for normal movement operation. This last operation 5 can be carried out after having fitted the movement or it can take place before the movement is nested.

(as described in the applicant's European patent application 11009678).

According to one embodiment, before putting the movement into a low-pressure atmosphere in step 1, the method includes the step of checking, and if necessary adjusting, the movement at atmospheric pressure so that it has a precision time clock of substantially zero seconds per day.

Advancing or retreating in step 2 is typically an advance, ΔΡ being positive, and the setting in step 4 is typically accomplished by backing -ΔΡ being negative.

Since the measurement carried out in step 3 of the process can be done optically, for example, through the wall of a vacuum chamber that is transparent or acoustically, it is not necessary to act on the movement while it is under vacuum. . This makes it unnecessary to provide complicated means of intervention in the vacuum chamber as is the case in known devices where the setting of the racket is under vacuum.

When a series of identical motions is to be set, a first movement of the motion series may be subjected to the tuning process described above. Then consider the variation in accuracy + ΔΡ time between the operation at atmospheric pressure and the gait under reduced pressure atmosphere as a standard correction standard to be applied to all other movements in the series of identical movements. Thus, for the second and subsequent movements of a series of identical movements, it is sufficient to adjust them to atmospheric pressure for chronometric precision. -ΔΡ compensation and then put these movements in an atmosphere, at the pre-established reduced pressure so that their chronometric accuracy is substantially zero seconds per day.

Thus when one has a series of identical motion to adjust this process allows a fast and easy time adjustment since it is sufficient to adjust each movement at atmospheric pressure to a standard value -ΔΡ and then put the movement in its box under pressure atmosphere reduced for normal operation.

In one example, practical tests carried out on a series of identical movements show a range of advance of the order of +12 s / d to +14 s / d between the operation under atmospheric pressure and the operation at the preset reduced pressure. for the normal operation of the movements.

By way of example, it may be mentioned that in measurements made on certain movements of a series of manufactured movements

the following results:

Movement 1 (not settled):

Amplitude at atmospheric pressure: 220 °

Amplitude at 1 mbar: 260 °

Operating at atmospheric pressure: +11 s / d

Walking at 1 mbar: + 24s / d

Delta walk: + 13s / d

Movement 2 (not settled):

Amplitude at atmospheric pressure: 220 °

Amplitude at 1 mbar: 268 °

Walk at atmospheric pressure: +3.4 s / d

Walking at 1 mbar: + 17s / d

Delta works: +13.6 s / d Movement 3 (not settled):

Amplitude at atmospheric pressure: 210 °

Amplitude at 1 mbar: 270 °

Walk at atmospheric pressure: -27 s / d

Operating at 1 mbar: -14.2 s / d

Delta works: +12.8 s / d

Movement 4 (set):

Amplitude at atmospheric pressure: 220 °

Amplitude at 1 mbar: 262 °

Operating at atmospheric pressure: 0 s / d

Walking at 1 mbar: +13.3 s / d

Delta walk: + 13.3s / d

The deltas between the different measurements vary between +13.6 s / d and +12.8 s / d, which is a variation of less than s / d. Taking the adjustment value Δ = -13.2 s / d for the ambient atmospheric pressure setting of all the movements of the series, we would have time lapse values varying between -0.4 s / d and 0.4 s / d, which is an excellent initial setting value for mechanical movement.

Thus, once the above-described measurements are made for a few samples of a given movement (for example between 1 to 5 movements) and this ΔΡ chronometry accuracy difference value is known for this movement, it can be used for the adjustment of many identical movements which greatly facilitates the adjustment process and also significantly reduces the time required for this adjustment. To maintain a good chronometry it is necessary to make the necessary offset before the vacuum which eliminates all the complications related to a setting to be performed under vacuum.

The evacuation or under a predetermined reduced-pressure atmosphere being quite fast, it is possible to put the movement under vacuum, measure its chronometry (+ xs / d), put the movement back to atmospheric pressure and set it to - xs / d, to have a step of zero s / d under vacuum. This vacuum or low pressure is preferably between 5 mbar and 0.1 mbar.

As these operations are relatively fast one can if one wants to achieve a very high chronometric accuracy, repeat for the adjustment of the same movement the operations 3, 4, 5 and 6 of the process until a chronometric accuracy in operates under reduced pressure atmosphere substantially equal to zero s / d. In doing so we always benefit from the fact that the operation of adjusting the chronometry of the movement is always done when the movement is at atmospheric pressure, which avoids complex tools.

Claims

1. Method for adjusting the chronometry of a mechanical clockwork movement intended to operate in an atmosphere at low pressure, characterized in that the following successive operations:

2. measuring the advance or the retreat (ΔΡ) of the chronometric accuracy of the movement at this low pressure,

3. return the movement to ambient atmospheric pressure,

4. adjust the movement to compensate for the advance or recoil previously measured in low pressure operation by moving forward or backward (-ΔΡ),

5. Return the movement to atmosphere at the pre-set low pressure for normal movement operation.

2. Method according to claim 1, characterized in that the operations 3, 4, 5 and 6 are repeated one or more times in succession to refine the chronometric adjustment in operation under reduced pressure, the timing of movement timing s' always performing when this movement is subject to the ambient atmosphere. Process according to Claim 1, characterized in that for the adjustment of a series of identical movements operations 1 to 5 are carried out on at least one sample of the said series of movements and then, for the subsequent movements of the series of movements, it is carried out only the operations 4 and 5, the measurement obtained by the operation 2 being considered as a standard value applied for all the movements of a series of identical movements.

Process according to Claim 3, characterized in that the sample or samples comprise at most 5 movements.

Method according to one of the preceding claims, characterized in that step 5 is carried out once the movement has been nested.

Method according to one of the preceding claims, characterized in that step 5 is performed before the movement has been engaged.

Method according to one of the preceding claims, characterized in that the low pressure is between 5 mbar and 0.1 mbar.

Method according to one of the preceding claims, characterized in that the advance or the retreat in step 2 is an advance, ΔΡ being positive, and the adjustment in step 4 is accomplished by reversing, - ΔΡ being negative.