EP3561612B1 - Method for assembling a timepiece - Google Patents

Description

The invention relates to a method for mounting or assembling a waterproof timepiece. The invention also relates to a timepiece, in particular a timepiece obtained by implementing such a process.

A variation of pressure on a watch movement modifies its rate. The variation is of the order of 0.01 to 0.02 seconds per day and per mmHg, or 10 to 15 seconds per day and per bar. This effect of pressure on the rate of the watch is used in particular to check the tightness of the case as described in the document EP3136189 .

The document CH702865A2 describes a diver's watch equipped with a purge valve.

The casing step of a movement in a waterproof watch case also influences the rate of the movement, because the locking of the back of the case induces an increase in the pressure within the case. This pressure equilibrates over time to become equal to the pressure of the environment outside the watch case. However, the adjustment of the bare movement, as it will have been presented for inspection or certification, for example to the COSC, is disrupted for a period of a few months, until the overpressure disappears. Once assembled, the watch therefore has a different rate from that of the bare movement.

• un premier volume libre interne à la boîte avec le fond posé et le joint d'étanchéité non compressé mais en contact avec les surfaces sur lesquelles il doit porter, et
• un deuxième volume libre interne à la boîte avec le fond bloqué et le joint d'étanchéité écrasé.

The casing-up step consists of placing the movement in its case, fixing it there, inserting the crown stem and then closing the caseback. The variation in pressure experienced by the movement during casing up corresponds to the change between:

• a first free volume internal to the box with the bottom installed and the seal uncompressed but in contact with the surfaces on which it must bear, and
• a second free volume internal to the box with the bottom blocked and the seal crushed.

The pressure variation therefore depends on the geometry of the box and the movement. For a watch with a diameter of approximately 40 mm, the variation in pressure linked to the closing of the back can induce a rate delay of nearly one second per day.

According to the document " Influence of entrained fluid on the period of oscillation of a torsion pendulum”, C. Attinger, Annual Bulletin of the SSC, 1947 , the period of oscillation of a pendulum is influenced by the surrounding gas. The on-pressure function is generally in the order of 0.01 to 0.02 s/d per mmHg, with a delay when the pressure increases. The larger the balance wheel, the smaller the rate variations.

According to the document " Influence of barometric variations on the rate of marine chronometers”, E. Guyot, Annual Bulletin of the SSC, 1938 , the effect of atmospheric pressure on the rate of a particular watch is characterized by its barometric coefficient C (variation of its rate per unit of pressure). It is considered constant with respect to the common temperatures of use of a watch, and must be measured for each timepiece (or each construction).

This effect is used in particular for checking the tightness of watch cases, as described in the patent application EP3121663 or by C. Attinger already in 1948 in the document “ Barometric pressure and watches. Miscellaneous Applications”, C. Attinger, Annual Bulletin of the SSC, 1948 .

The measurements carried out on different calibers to assess the rate variation as a function of the pressure show a variation of more than 10 seconds per day for a difference of 1 bar and also confirm that the cased movement is practically no longer subject to atmospheric variations. A stabilization time could be estimated at three months for the pressures outside and inside a watch case to balance and for the rate to stabilize.

If the advent of waterproof watches has had the advantage of allowing their portability in the most diverse environments, it has resulted in the introduction of a new problem: the variation of the rate between the movement as it will have been regulated, see controlled by the COSC, and the movement in watch, closed back.

Indeed, the closing of the bottom of a sealed box induces an increase in pressure within the box, which can go up to almost 0.1 bar, that is to say a difference in rate due to the blocking of the bottom of one second per day.

Theoretical pressure calculations are set out below for a watch case having a back screwed onto the middle.

• p1 : la pression environnant la boîte de montre au moment où l'environnement intérieur à la boîte de montre est isolé de l'environnement extérieur à la boîte de montre ;
• V1 : le volume libre à l'intérieur ou le volume de gaz de l'environnement intérieur à la boîte au moment où l'environnement intérieur à la boîte de montre est isolé de l'environnement extérieur à la boîte de montre ;
• p2 : la pression interne à la boîte de montre ou de l'environnement intérieur à la boîte de montre une fois que le premier élément est complètement monté et serré sur la carrure ;
• V2 : le volume libre à l'intérieur ou le volume de gaz de l'environnement intérieur à la boîte une fois que le premier élément est complètement monté et serré sur la carrure.

The pressure within a waterproof watch case obeys the Boyle-Mariotte law: p1.V1 = p2.V2
with

• p1: the pressure surrounding the watch case when the environment inside the watch case is isolated from the environment outside the watch case;
• V1: the free volume inside or the gas volume of the environment inside the box at the moment when the environment inside the watch case is isolated from the environment outside the watch case;
• p2: the pressure internal to the watch case or of the environment inside the watch case once the first element is completely mounted and tightened on the middle part;
• V2: the free volume inside or the volume of gas from the interior environment to the box once the first element is completely mounted and tightened on the caseband.

avec :

• d : le diamètre extérieur du filet du fond ;
• h : la différence de hauteur du premier joint d'étanchéité entre la configuration où l'environnement intérieur à la boîte de montre est isolé de l'environnement extérieur à la boîte de montre et la configuration une fois que le premier élément est complètement monté et serré sur la carrure.

If the atmospheric pressure p1 (for example 0.966 bar) is associated with the volume V1 of the case comprising the movement, case back installed, the pressure variation Δp is given by the equation: $$\Delta \mathrm{p}=\mathrm{p1}\mathrm{.}\Delta \mathrm{V/V2}\mathrm{with}\Delta \mathrm{V}=\mathrm{\pi }.\mathrm{h}.{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">d</figure-callout>}}^2/4$$

with :

• d: the outer diameter of the bottom thread;
• h: the difference in height of the first seal between the configuration where the environment inside the watch case is isolated from the environment outside the watch case and the configuration once the first element is completely mounted and tightened on the middle part.

For example, closing the back of a watch with a diameter of 40 mm, comprising a back with a thread diameter of 32 mm, the sealing of which is ensured by an O-ring with a torus diameter of 0.8 mm, will cause a pressure difference of 0.028 bar when locking the back. This difference will induce a rate variation of approximately 0.3 seconds per day.

For waterproof watches, it is considered that the balance can be achieved by diffusion of the air through the seals, and that an adjustment of the rate at sea level will be compensated quickly if its owner is at altitude. However, it could prove advantageous, both at the level of the factory setting and during subsequent operations, to ensure that the setting made by the watchmaker is maintained. This is the This is particularly the case at the level of after-sales service, where the customer risks observing a significant difference in rate in the first months following an intervention on his watch due to the variation in pressure in the watch case.

It would be possible to alleviate the problem by anticipating this pressure variation and adjusting the rate of the movement accordingly, so as to guarantee adequate rate once the movement is fitted, just after fitting, but this requires a complex calculation and is only difficult to apply in after-sales service. Moreover, a few months after the intervention, the pressures having balanced, walking would then be unsuitable.

The object of the invention is to provide a method for mounting or assembling a sealed timepiece making it possible to remedy the drawbacks mentioned above and to improve the known methods of the prior art. In particular, the invention proposes a simple mounting method which makes it possible to improve the chronometric precision of the timepieces thus mounted.

An assembly method according to the invention is defined by claim 1.

Different embodiments of the assembly method are defined by claims 2 to 12.

Timepieces according to the invention are defined by claims 13 to 15.

• Les figures 1 à 4 sont des vues en coupe d'un mode de réalisation de la pièce d'horlogerie dans différentes configurations.
• La figure 5 est vue en coupe d'une première variante du mode de réalisation de la pièce d'horlogerie dans différentes configurations.
• La figure 6 est vue en coupe d'une deuxième variante du mode de réalisation de la pièce d'horlogerie.

The appended figures represent, by way of example, an embodiment of a timepiece according to the invention.

• THE figures 1 to 4 are cross-sectional views of one embodiment of the timepiece in different configurations.
• There figure 5 is a sectional view of a first variant of the embodiment of the timepiece in different configurations.
• There figure 6 is a sectional view of a second variant of the embodiment of the timepiece.

A first embodiment of a timepiece 1 is described below with reference to the figures 1 to 4 . The timepiece is for example a watch, in particular a wristwatch. The timepiece comprises a movement 2. The movement is a mechanical movement. The movement can in particular be an automatic mechanical movement.

The timepiece also includes a watch case, in particular a waterproof watch case. The watch case is intended to enclose the movement in a watertight manner. Thus, the watch case defines an environment 4 inside the watch case isolated from an environment 5 outside the watch case.

The watch case comprises a middle part 33 closed on a first side by a crystal and on a second side by a first case element, for example by a bottom 31. It also comprises the element or elements necessary for fixing the second case element, for example a crown tube.

The seal between the middle part and the first element is ensured by a first seal 34.

The first element can be mounted screwed onto the middle part, that is to say the first element can be linked by a helical connection to the middle part. Alternatively, the first element can be mounted using screws on the caseband. Preferably, the mounting of the first element compresses or crushes the first seal. This compression or this crushing of the first seal causes a reduction in the volume inside the watch case. Assuming that, from the continuous contact over the entire circumference of the first seal with the first element, the interior environment 4 of the watch case is insulated, the deformation, in particular the compression or the crushing of the first seal causes an increase in the pressure in the interior environment of the watch case, if it is assumed that the watch case is not open in another place.

The box is further closed by a second box element. In particular, in the embodiment shown in the figures 1 to 4 , the second element is a winding crown 320 associated with a stem 321 passing through the caseband, in particular a crown stem passing through the caseband.

The second element is a movable element, in particular movable between a first configuration and a second configuration. These two configurations can be reached via different positions of the second element. The second element is for example movable longitudinally, that is to say along the longitudinal direction of the second element. THE figures 1, 2 And 3 illustrate first configuration positions. There figure 4 illustrates a position corresponding to the second configuration.

The second element is arranged so that in the second configuration, the second element is able to seal the case and arranged so that in the first configuration, the second element is able to allow fluid communication between the interior 4 of the watch case and the environment 5 outside the watch case.

The second element crosses for example the middle part. The watchcase also includes a second seal 35. The second seal cooperates with the second element to seal the watchcase at the interface between the second element and the middle part.

The state of the second seal can define the tightness and the configuration of the second element. Thus, when the second seal is in contact only with one of the parts at the interface of which it is intended to provide sealing, the interior of the watch case is in fluid communication with the exterior and the second element is therefore in the first configuration. When the second gasket is in contact with the two parts at the interface of which it is intended to provide sealing and it is compressed between these two parts, the interior of the watch case is insulated from the outside, the case is then sealed, and the second element is in the second configuration. Finally, between these two configurations, it is possible to define a limit configuration in which the second seal is just in contact with the two parts at the interface of which it is intended to provide sealing, without it being compressed between these two parts. In this limit configuration, one can speak of a partial watertightness of the watch case.

The second seal is for example a second O-ring. This second seal is, for example, housed in a groove in the middle part or in a part necessary for fixing the second element, attached to the middle. Alternatively or additionally, a second seal can be housed in a groove of the second element. Alternatively or additionally, a second seal can be housed in a cap bottom of the second element, in particular at the bottom of a crown.

The second element is, in the second configuration, in a situation of contact with the second seal 35 and, in the first configuration, in a situation of broken or partially broken contact with the second seal.

Preferably, the second element has a portion 321 of reduced section intended to come face to face with the second seal 35 in the first configuration of the second element. The reduced section portion may comprise a first groove or a first groove made on the second element.

The second element comprises a rod, this rod has for example a shape of revolution, in particular the rod is preferably generally cylindrical of revolution. The second element may comprise a stem and a crown secured to the stem. Alternatively again, the second element may comprise a rod and a cap secured to the rod.

This rod has a second groove or second groove 322 intended to cooperate with a pull tab 21, in particular intended to cooperate with a stud 22 of the pull tab. In particular, the second groove is provided to receive the pull stud. Thus, the position of the zipper can be controlled by the position of the rod, by action of the second groove on the pull stud.

In a variant of the embodiment of the timepiece, which does not form part of the invention, shown in the figure 5 , the second element is a stem 32A of a valve 39. In this variant, the stem 32A is screwed onto the middle part 3 and can be moved in a helical connection between a first configuration where there is play between the stem and the middle part ( figure 5 , right view) and a second configuration where sealing between the stem and the caseband is ensured ( figure 5 , left view), in particular ensured by means of a joint 35A. Stem 32A can be screwed onto caseband 3 and can be moved in a helical connection, via a cap integral with the second element or forming part of the second element.

In a second variant of the embodiment of the timepiece, which does not form part of the invention, represented on the figure 6 , the second element is also a stem 32A of a valve 39. In this variant, the stem 32A is slidably mounted in the middle part, in particular pivot-mounted sliding in the middle part 3. A spring, in particular a spring arranged inside the watch case, brings the stem back into a second configuration where the seal between the stem and the middle part is ensured ( figure 6 ) in particular by the action of a second seal. The stem has a head on the outside of the watch case. This head is shaped to be manipulated by a user or a watchmaker, via a tool 40. Indeed, using the tool 40, it is possible to act on the stem head, in particular to pull on the stem head, against the spring, so as to bring the stem into a first configuration where there is play between the stem and the caseband.

These two previous variants can in particular be adapted to diver's watches in which an improved watertightness is achieved at the crown stem-middle interface and/or comprising a seal at the level of the crown.

In a third variant of the embodiment of the timepiece, not shown, the second element may be a stem of a pusher.

An embodiment of a method for assembling a timepiece is described below.

In a first step, movement 2 is fitted, that is to say, the movement is integrated into the watch case. This operation is carried out for example by a watchmaker during the production of the timepiece or by a watchmaker during an after-sales service operation. The first step aims to insert and fix the movement in a waterproof watch case so as to allow adjustment of the movement. It includes in particular the insertion of a rod allowing the various manipulations of the movement to be carried out. This rod can be a working rod, which is removed before screwing the bottom and which is replaced by a final rod once the bottom is screwed.

Once the movement has been fitted, in a second step, the movement is adjusted. In particular, the rate of the movement is adjusted.

In a third step, the rate M1 of the nested movement is measured.

In a fourth step, the second element is positioned in a first configuration in which fluid communication between the interior 4 of the box and the environment 5 outside the box is permitted. In particular, in the first configuration, the reduced section portion 321 of the stem comes face to face with the second seal 35. The seal is in contact with only one part, either the box or the second element.

The movement to put the second element in the first configuration is authorized by an action of the watchmaker on a third element of the watch movement, in particular by an action on the pull tab 21, in particular on the stud 22 of the pull tab. This step can therefore only be implemented with the bottom of the box deposited. This step therefore cannot be implemented by the wearer of the watch. As a variant, it is possible to completely remove the winding stem, in particular when the watchmaker uses a working stem and he replaces the working stem with a final stem after fixing the first element.

In order to implement the fourth step in a safe manner, a suitable laying is preferably used. This mounting comprises for example a stopper making it possible to limit the withdrawal of the stem from the movement and to ensure that the stem comes perfectly into the first configuration. This stop therefore defines a position corresponding to the first configuration, position by which the rod remains engaged in the pinions and wheels of the systems operating using the rod. Preferably, the first configuration can be reached after complete insertion of the stem into the movement, or at least after deeper insertion of the stem into the movement. As a variant, the rod, in particular the working rod, could be completely withdrawn from the movement to reach the first configuration. However, this solution is more risky because it requires subsequent insertion of the final stem without being able to ensure visually that it engages well in the sliding pinion, and therefore requires a certain skill.

In the event that the second element is a valve stem 32A 39 as shown in the figure 6 , the fourth step is carried out by the watchmaker with the aid of a tool 40, in particular a tool making it possible to operate a valve of the case. This fourth step is then implemented after the box closing steps.

In a fifth step, the box is closed by putting in place and locking the first box element 31, in particular the bottom 31. Closing the box can include screwing the bottom 31 onto the middle part 33 or mounting the bottom using screws. The blocking of the back on the middle part 33 deforms, in particular compresses, the first seal 34.

In a sixth step, the box is closed by actuating the second element 32. The actuation of the second element allows it to pass from its first configuration to a second configuration in which the fluid communication between the interior 4 of the box and the environment outside 5 of the box is limited. The seal 35 is brought into contact with the two parts: the box and the second element. Ideally, for example by a screwing action of the crown, the seal 35 is compressed to guarantee greater sealing.

In this second configuration, the fluid communication between the interior 4 of the box and the environment 5 outside the box is limited as much as possible. This fluidic communication can be limited sufficiently so that the watch case can be waterproof, in particular waterproof to 100 m or 300 m or 1220 m according to the standards NIHS 92-10 (1986) or NIHS 92-11 (1996). In particular again, this fluid communication can be limited sufficiently to be less than or equal to 50 μg/min for air with a pressure difference of 2 bars between the environment 4 inside the watch case and the environment 5 outside the watch case.

The actuation of the second element 32 may comprise a displacement of the second element from the first configuration to the second configuration, in particular a longitudinal displacement of the stem, in particular of the winding stem. This actuation can also be done by means of a helical movement (screwing of the crown which compresses a seal).

• un passage du premier élément d'une troisième configuration, dans laquelle une communication fluidique entre l'intérieur 4 de la boîte et un environnement extérieur 5 à la boîte est permise, à une quatrième configuration, dans laquelle la communication fluidique entre l'intérieur 4 de la boîte et l'environnement extérieur 5 à la boîte est limitée, en supposant que ce passage de la troisième configuration à la quatrième configuration rende étanche ou hermétique cette boîte de montre, ou
• la mise en place et le blocage du premier élément sur le reste de la boîte.

The second element 32 is preferably arranged so that the passage from the first configuration to the second configuration of the second element causes an increase in pressure in the box less than or equal to 5%, in particular of the order of 2%, of the increase which would be caused by:

• a passage of the first element from a third configuration, in which fluid communication between the interior 4 of the case and an environment 5 outside the case is permitted, to a fourth configuration, in which the fluid communication between the interior 4 of the case and the environment 5 outside the case is limited, assuming that this passage from the third configuration to the fourth configuration renders this watch case watertight or hermetic, or
• the placement and blocking of the first element on the rest of the box.

• un passage du premier élément de la troisième configuration, dans laquelle une communication fluidique entre l'intérieur 4 de la boîte et l'environnement extérieur 5 à la boîte est permise, à la quatrième configuration, dans laquelle la communication fluidique entre l'intérieur 4 de la boîte et l'environnement extérieur 5 à la boîte est limitée, en supposant que ce passage de la troisième configuration à la quatrième configuration rende étanche ou hermétique cette boîte de montre, ou
• la mise en place et le blocage du premier élément sur la boîte ou sur le reste de la boîte.

In other words, the second element 32 is preferably arranged so that the passage from the first configuration to the second configuration of the second element causes a displacement of fluid in the box less than or equal to 25%, or even less than or equal to 10%, or even less than or equal to 5% of the fluid displacement caused by:

• a passage from the first element of the third configuration, in which fluid communication between the interior 4 of the case and the environment 5 outside the case is permitted, to the fourth configuration, in which the fluid communication between the interior 4 of the case and the environment 5 exterior to the case is limited, assuming that this passage from the third configuration to the fourth configuration seals or seals this watch case, or
• the placement and blocking of the first element on the box or on the rest of the box.

The second element 32 is for example arranged so that the passage from the first configuration to the second configuration causes an increase in pressure in the box, less than or equal to 0.1% or less than or equal to 0.5% and/or causes a reduction in the free volume inside the box less than or equal to 0.5% or less than or equal to 0.2% and/or causes a rate variation considered to be zero.

• une position limite du deuxième élément où l'étanchéité de la boîte de montre est juste réalisée, notamment le joint étant juste au contact des parties à l'interface desquelles il doit assurer l'étanchéité, sans compression du joint ;
• une deuxième position du deuxième élément dans laquelle le volume déplacé est maximisé ou une deuxième position du deuxième élément dans laquelle le deuxième élément se trouve en usage normal de la montre (par exemple configuration de couronne vissée). Dans cette deuxième position, le joint est au contact des parties à l'interface desquelles il doit assurer l'étanchéité et il est comprimé pour assurer un degré d'étanchéité suffisant.

Preferably, the volume of gas displaced by the second element 32 in the watch case is less than or equal to 40 mm ³ , even less than or equal to 30 mm ³ , even less than or equal to 10 mm ³ , even less than or equal to 1%, even less than or equal to 0.5%, of the free volume in the watch case. The volume of gas displaced is defined between:

• a limit position of the second element where the tightness of the watch case is just achieved, in particular the gasket being just in contact with the parts at the interface of which it must ensure the tightness, without compression of the gasket;
• a second position of the second element in which the displaced volume is maximized or a second position of the second element in which the second element is in normal use of the watch (for example screw-down crown configuration). In this second position, the seal is in contact with the parts at the interface of which it must ensure sealing and it is compressed to ensure a sufficient degree of sealing.

In the second configuration, the second element is preferably in a contact condition with the second seal 35 and, in the first configuration, the second element is preferably in a broken or partially broken contact condition with the seal.

In a seventh step, the rate M2 of the movement enclosed in the watch case is measured. The rate measurement step can be part of a box leak test.

In an eighth optional step, the steps M1 and M2 measured during the previous steps are compared.

The assembly method described makes it possible, in the case of a watertight watch case, to retain the adjustment of the movement as it was done outside the case, or in-situ in the movement, before closing the back. Generally and simply, the second element is removed before or after closing the first box element and the second box element is inserted again or a new box element is inserted later, in any case once the first box element has been put in place and fixed. In a safer and more elegant way, it is also possible to provide a specific position corresponding to the second configuration, accessible only by an action of the watchmaker on the pull stud, and which guarantees that the second winding stem type element remains inserted at its end. In this specific position, the stem can be inserted at its end into one or more pinions of a stem mechanism, in particular a sliding pinion, while ensuring that a portion of stem of a predetermined diameter is placed at the level of the stem hole formed on the middle part when the case back is closed, so as to allow air to pass between the middle part and the stem. This position can be precisely determined by means of assembly laying. This position is preferably a position separate from the stem positions enabling the watchmaking functions of winding and correction to be performed, in particular time correction, time zone correction, date correction.

Indeed, in several traditional constructions of winding crowns, a (limited) water resistance is maintained even in adjustment mode. A constant crown stem section cooperates with a seal to compress the latter, in the different positions of the stem dedicated to winding ( figure 1 ) and the various corrections ( figure 2 And 3 ).

The assembly process and any fitting adapted to the process make it possible to achieve the objectives. The rod can be inserted normally by the watchmaker to adjust the movement. When he wishes to close the bottom, he can, by means of an action on the pull stud and the use of the appropriate fitting, withdraw the rod to the specific position. In this specific position, the thin part or part of the reduced section of the stem is at the level of the joint 35. The back can then be closed and locked without inducing an increase in pressure, and the watchmaker can then insert the stem completely into the movement without risk. The zipper stud makes it possible to prevent the wearer from does not withdraw the rod too far and the tightness of the case is lost, this tightness being preferably guaranteed also in the adjustment or correction positions.

Alternatively, as seen previously, the working stem can be removed by action on the pull stud, before screwing on the bottom and subsequently fitting a final stem of the product. The final rod is fitted with the bottom closed, taking care to engage it correctly in the sliding pinion.

The first stem configuration may comprise the position of the stem furthest drawn out of the caseband. The first stem configuration may include a stem position in which the crown is unscrewed.

Preferably, the first stem configuration may comprise a stem position in which the crown is unscrewed and/or a stem position allowing the movement to be wound and/or at least one stem position allowing correction, in particular a stem position allowing date correction and/or a stem position allowing time zone correction and/or a stem position allowing time correction.

Preferably, the first configuration can comprise several positions of the second element and/or the second configuration can comprise several positions of the second element.

The second stem configuration can comprise a stem position in which the crown is screwed down or the most depressed position of the stem in the caseband.

The second element can be arranged unidirectionally movable from the first configuration to the second configuration. In particular, the second element can be arranged to move from the second configuration to the first configuration by means of the action of a watchmaker on the movement and/or the second element can be arranged to move freely from the first configuration to the second configuration.

The problem solved by the method described above arises for watches for which the adjustment precision required is high. Indeed, the rate variation induced by the pressure variation is negligible for most watches, a fortiori for watches that do not have a reliable sealing system at the level of the winding crown.

Claims (15)

1. Method of assembling a timepiece (1) comprising a watch movement (2) and a water-resistant case (3), the method comprising the following stages:

   - a first stage of closing the case by fitting and securing a first case element (31), more particularly a back (31), and then

   - a second stage of closing the case by actuation of a second case element (32), the second case element (32) being a winding stem (32), the second case element (32) being mobile between a first configuration, in which a fluid communication between the interior (4) of the case and an environment (5) outside the case is permitted, and a second configuration adapted to ensure the sealing integrity of the case,

   the second stage of closing being an actuation of the passage of the second element from the first configuration to the second configuration.
2. The method of assembling as claimed in the preceding claim, wherein the second element (32) is arranged so that the passage from the first configuration to the second configuration of said second element causes a displacement of fluid inside the case of less than or equal to 25%, or even less than or equal to 10%, or even less than or equal to 5%, of the displacement of fluid caused by:

   - passage of the first element from a third configuration, in which a fluid communication between the interior (4) of the case and the environment (5) outside the case is permitted, to a fourth configuration, in which the fluid communication between the interior (4) of the case and the environment (5) outside the case is limited enough so that the case (3) is water-resistant to 100 m or 300 m or 1220 m; or

   - positioning and securing the first element on the case.
3. The method of assembling as claimed in one of the preceding claims, wherein it comprises a third stage of testing the sealing integrity of the case (3) subsequently to the second stage, more particularly a third stage of testing the sealing integrity of said case in which a value for the rate of the movement is measured.
4. The method of assembling as claimed in one of the preceding claims, wherein it comprises, prior to the first stage, a stage of adjusting the rate of the movement.
5. The method of assembling as claimed in one of the preceding claims, wherein the first stage of closing the case (3) comprises screwing a back (31) onto a case middle (33).
6. The method of assembling as claimed in the preceding claim, wherein screwing the back (31) onto the case middle (33) deforms, in particular compresses, a first sealing gasket (34).
7. The method of assembling as claimed in one of the preceding claims, wherein the second stage of closing the case (3) comprises a displacement of the second element (32) from the first configuration to the second configuration.
8. The method of assembling as claimed in one of the preceding claims, wherein the second element (32), in the second configuration, is in a situation of contact with a second sealing gasket (35) and, in the first configuration, in a situation of interrupted contact or partially interrupted contact with said second sealing gasket.
9. The method of assembling as claimed in one of the preceding claims, wherein the second element (32) is a stem and wherein, in the first configuration, said stem exhibits a portion (321) of reduced cross section facing the second sealing gasket (35).
10. The method of assembling as claimed in one of the preceding claims, wherein it comprises a fourth stage of actuation of the second case element (32) so as to position said second case element in the first configuration, the third stage being prior to the first stage.
11. The method of assembling as claimed in one of the preceding claims, wherein a displacement in order to place the second element (32) in the first configuration requires an action on a third element (21) of the watch movement, more particularly action on a pull-out piece (21).
12. The method of assembling as claimed in one of the preceding claims, wherein a displacement in order to place the second element (32) in the second configuration is performed independently of an action on a third element (21) of the watch movement, more particularly independently of an action on a pull-out piece (21).
13. The timepiece (1), more particularly a wristwatch, comprising a movement and a watch case (3) comprising a winding stem (32), said stem being arranged so as to be mobile between a second configuration adapted to ensure the sealing integrity of the case and a first configuration adapted to permit fluid communication between the interior (4) of the watch case and an environment (5) outside said watch case.
14. The timepiece as claimed in the preceding claim, wherein the stem (32) is a stem exhibiting a portion (321) of reduced cross section intended to come into a position facing a sealing gasket (35) in the first configuration of the stem, and/or wherein the stem is arranged to be movable unidirectionally from the first configuration to the second configuration, and/or wherein the stem is arranged to be movable from the second configuration to the first configuration by the action of a watchmaker on the movement, and/or wherein the stem is arranged to be freely movable from the first configuration to the second configuration.
15. The timepiece (1), more particularly a wristwatch, obtained by the implementation of the method as claimed in one of claims 1 to 12.

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