EP3226080A1 - Barrel system for a timepiece - Google Patents

Abstract

System (1) for a timepiece cylinder, said system (1) comprising: - a barrel (3) comprising a barrel shaft (7), a barrel drum (5) coaxial with said shaft (7); - a barrel spring (15) disposed within said barrel (3), said spring (15) being connected by a first end (15a) to said shaft, and connected by a second end (15b) to said barrel by the intermediate of a flange that comprises said second end (15b) of said barrel spring (15), said spring (15) comprising a first layer of amorphous carbon (17) of a first type on at least a part of its surface. According to the invention, at least one component (5, 7, 11) of said barrel (3) comprises a second layer of amorphous carbon (19) of a second type, different from said first type, on at least a part of its surface intended to be in contact with said barrel spring (15), said first layer (17) and said second layer (19) being arranged to contact at least a portion of their respective surfaces. Moreover, said second layer (19) differs from said first layer (17) with respect to the hybridization proportions of the carbon atoms in each of said layers (17, 19).

Description

Technical area

The present invention relates to the field of watchmaking. It relates, more particularly, a self-lubricating cylinder system for a timepiece.

State of the art

In a traditional mechanical watch, the energy for its operation is typically stored in one or more barrels acting as a driving source for the regulating organ. This energy is transmitted between the barrel and the regulating member by means of a finishing train, which is also used to drive the display members.

A conventional barrel has a hollow drum coaxial with a barrel shaft, and a lid that serves to close the drum. Inside the drum is a spiral barrel spring that connects the shaft to the inside wall of the drum. In order to ensure the connection between the outer end of the spring and the drum, the first is provided with a flange, attached to, or integral with, said outer end. This flange can be of the fixed type, which is typically intended for a manual winding watch, or sliding, which is typically intended for a self-winding watch. In order to operate the timepiece, the spring is armed and applies a torque allowing maintenance of the movement by unwinding. If the torque provided by the spring is not sufficiently constant, the isochronism of the watch is not assured.

Inside the barrel, there are several surfaces that come into contact with each other and therefore generate friction. For example, the turns of the spring may rub together, the flange and the outer coil may rub against the inner wall of the drum, and the upper and lower faces of the spring may rub against the cover and / or against the flat inner face of the spring. drum.

In order to limit this friction, the barrel is traditionally greased. Such lubrication, usually organic, is very sensitive to external factors such as changes in temperature, slight variations in moisture, and chemical changes in fat that occur over time. These, which lead to a degradation of tribological properties of the lubricant, require that the barrel is subjected to regular periodic maintenance, typically a period of a few years. Such maintenance requires dismantling of the part, as well as complete disassembly and cleaning of the barrel and the spring.

Some solutions have already been presented to avoid the use of a wet lubricant, by reducing the coefficient of friction between the elements of the barrel system that rub against each other (such as the flange and the drum wall) by depositing self-lubricating materials on at least one of these components. In this respect, the document GB 864 531 reveals a barrel spring coated with a thin layer (<1μm) of a synthetic resin or plastic which constitutes a dry lubricant. The documents US 2,979,417 and GB 987 702 propose similar solutions. The document FR 1,249,231 proposes, on the other hand, to use a layer of a stearic acid salt for the same purpose, and the document EP 2 270 612 offers a polycrystalline diamond coating. Finally, the documents WO 02/204836 , WO 2013/011032 and US 6,755,566 provide a diamond-like carbon (DLC) deposit, which is a form of amorphous carbon, on a barrel spring, or on the wall of a barrel drum, if any. In the case of the document WO 2009/043391 the two barrel spring surfaces which come into contact with each other are each provided with a layer of DLC, each layer of which has a different orientation of the crystalline planes.

While these dry lubrication solutions represent tribological advances over a greased standard barrel, they are not quite satisfactory in the coefficient of friction and wear of the components that slide over each other. are therefore subject to friction. Therefore, a supply of fat sometimes remains necessary to maintain satisfactory operating conditions.

The object of the invention is therefore to provide a barrel system in which the aforementioned defects are at least partially overcome.

Disclosure of the invention

More specifically, the invention relates to a barrel system for a timepiece. This system comprises a barrel comprising a barrel shaft, a barrel drum coaxial with said shaft, and a barrel spring disposed inside said barrel. The drum may, if necessary, be closed by a cover. In known manner, said spring is connected by a first end, internal to said shaft, and connected by a second end, external, to said drum via a flange. The latter also comprises a first layer of amorphous carbon, of a first type, on at least a portion of its surface.

According to the invention, at least one component of said barrel, such as for example the inner cylindrical wall of the drum, the surface of the lid (if present) and / or the drum facing the spring, a bung arranged on the shaft, comprises a second layer of amorphous carbon, of a second type different from said first type, on at least a portion of its surface intended to be in contact with said mainspring. Said first layer and said second layer are arranged to at least partially contact each other, and have differences in terms of sp ² -sp ³ hybridization proportions of their carbon atoms.

Surprisingly, the use of two amorphous carbon layers have dissimilarities in terms of sp ² -sp ³ hybridization ratios of their carbon atoms substantially reduces the coefficient of friction and, therefore, avoids any application of fat. As a result, the system's performance and life are improved, and the system is easy to install because no grease has to be applied.

Advantageously, said first layer is disposed on at least a portion of said spring flange and / or at least a portion of the turns of said spring. Moreover, said second layer is advantageously disposed on at least a portion of the inner wall of the drum, and / or at least one part of the flat inner face of said drum in front of said spring and / or at least a portion of a bung that includes said shaft, and / or at least a portion of a surface of said lid facing said spring.

In one embodiment, said first layer is disposed on the spring flange as well as on the surface of the turns of the spring, said second layer being disposed (i) on at least a portion of the inner wall of the drum and is intended to be in contact with said first layer on the flange and (ii) on a bung which includes the barrel shaft and to which the inner end of the spring is bonded.

In another particular embodiment, said first layer is disposed on said spring flange as well as on the outer surface of the turns of the spring (that is, the surface facing the drum wall), said second layer being disposed on at least a portion of the inner wall of the drum and is intended to be in contact with said first layer, a third layer of amorphous carbon, of a third type different from said first type, is disposed on the inner surface of the turns of the spring (that is, the surface facing the barrel shaft). Said third type is preferably identical or substantially similar to said second type, but it may also be different from the two types mentioned above.

Therefore, the advantages of the invention can be obtained not only at the contact between the flange and the wall of the drum, but also between the turns of the spring. Moreover, a fourth layer of amorphous carbon, of a fourth type different from said third type, can be arranged on a bung which comprises the barrel shaft and to which the inner end of the spring is linked, said fourth type being preferably substantially similar to said first type. The invention can therefore be applied to any contact between the spring, the drum wall and the shaft.

Advantageously, one of said first layer and said second layer has a higher proportion of sp ³ hybridization carbon atoms than that of the other layer. Tests showed a preference for a higher proportion of sp ³ hybridization for the first layer, i.e., on the spring, relative to the proportion of sp ³ hybridization in the second layer.

Advantageously, the proportions of sp ² -sp ³ hybridizations of one of said first layer and said second layer are between 5% and 40% of sp ² hybridization carbon atoms and between 60% and 95% of sp ² hybridization carbon atoms. sp ³ hybridization carbon atoms, while the proportions of sp ² -sp ³ hybridizations of the other layer are between 60% and 90% of sp ² hybridization carbon atoms and between 10% and 40% sp ³ hybridization carbon atoms. More particularly, the proportions of sp ² -sp ³ hybridizations of one of said first layer and said second layer are between 5% and 20% of sp ² hybridization carbon atoms and between 80% and 95% of sp ³ hybridization carbon atoms, while the sp ² -sp ³ hybridization proportions of the other layer are between 65% and 75% sp ² hybridization carbon atoms and between 25% and 35% sp ³ hybridization carbon atoms.

In the case of a system comprising a third and a fourth layer as mentioned above, the proportions of sp ² -sp ³ hybridizations of one of said third layer and said fourth layer may be between 5% and 40%. % of sp ² hybridization carbon atoms and between 60% and 95% of sp ³ hybridization carbon atoms, while the proportions of sp ² -sp ³ hybridizations of the other of said third layer and said fourth layer may be between 60% and 90% sp ² hybridization carbon atoms and between 10% and 40% sp ³ hybridization carbon atoms. More particularly, the proportions of sp ² -sp ³ hybridizations of one of said third layer and said fourth layer may be between 5% and 20% of sp ² and 80% hybridization carbon atoms. and 95% sp ³ hybridization carbon atoms, while the sp ² -sp ³ hybridization proportions of the other layer may be between 65% and 75% sp ² hybridization carbon atoms. and between 25% and 35% of sp ³ hybridization carbon atoms.

Advantageously, each of said layers has a thickness of between 100 nm and 3 μm, preferably between 250 nm and 950 nm.

Brief description of the drawings

• La fig. 1 est une vue schématique en coupe d'un système de barillet selon un mode de réalisation exemplaire de l'invention ;
• La fig. 2 est une diagramme de phase ternaire du carbone amorphe ;
• La fig. 3 est une vue schématique d'un détail du principe de l'invention sous forme schématique ; et
• Les fig. 4 et 5 sont des vues schématiques de variantes de l'invention.

Other details of the invention will appear more clearly on reading the description which follows, given with reference to the appended drawings in which:

• The Fig. 1 is a schematic sectional view of a barrel system according to an exemplary embodiment of the invention;
• The Fig. 2 is a ternary phase diagram of amorphous carbon;
• The Fig. 3 is a schematic view of a detail of the principle of the invention in schematic form; and
• The Fig. 4 and 5 are schematic views of variants of the invention.

Embodiments of the invention

The figure 1 schematically illustrates an exemplary barrel system 1 according to the invention. With regard to the overall construction of the barrel system 1, it is quite conventional, one can take any known construction. In the variant shown, the system 1 comprises a barrel 3, the latter comprising a drum 5 rotatably mounted and coaxial with reference to a barrel shaft 7 in a known manner. The drum 5 carries a peripheral toothing 9, but can also be smooth to be used in combination with a rocket system. The drum 5 is typically closed by means of a lid 11, which can be secured to either the drum 5 or to the barrel shaft 7. A ratchet wheel 13 is also provided, integral in rotation with the barrel shaft 7 According to a known construction variant, the ratchet wheel 13 can be positioned on the shaft 7 in order to act as a cover 11.

Inside the barrel 3, in the space defined by the drum 5 and the lid 11 is housed a barrel spring 15. The inner end 15a of the spring 15 is connected to a plug 14 arranged on the shaft, and its outer end 15b has a flange which links it to the cylindrical inner wall 5a of the drum 5, in a known manner. The flange 15b may be integral with the spring 15, or may be an additional piece attached to the outer end in a known manner.

The main sources of friction in such a cylinder are as follows. First, each of the turns of the spring 15 can rub against its neighbor turn when the spring is unwound. The flange 15a and the outer coil of the spring 15, the inner end 15a of the spring 15 can rub against the bung 14 of the shaft 7. Moreover, if the spring 15 can bear against the flat inner face 5b or the face of the cover 11 opposite the spring 15, this can also cause friction. At least a portion of the spring 15 and a portion of the barrel 3 are coated with a self-lubricating layer, as will be explained in more detail later.

Before detailing the way in which the self-lubricating layers of the system 1 according to the invention differ from those of the prior art, the properties of the amorphous carbon (DLC) must first be examined.

For this purpose, figure 2 schematically represents a phase diagram of the amorphous carbon. The carbon atoms can be organized according to several different geometries, having different covalent bond orientations. In the crystalline diamond, the atoms are organized in a cubic face-centered structure, in which the covalent bonds are oriented according to tetrahedra. These bonds involve sp ³ hybridization carbon atoms, and this diamond structure is on the top tip of the diagram. In the case of graphite, atoms are organized according to leaflets. In each leaflet, the covalent bonds are oriented in regular hexagons lying in a single plane, and each leaflet is bound to its neighbor by Van der Waals forces. The hybridization of the carbon atoms in each sheet is of sp ² type. This structure is on the left tip of the diagram. The third, straight point of the diagram represents hydrogen.

• a-C : carbone amorphe substantiellement dépourvu d'hydrogène et présentant une hybridation dominante du type sp² (typiquement 60-90% sp² et 10-40% sp³) ;
• ta-C : carbone amorphe tétraédrique substantiellement dépourvu d'hydrogène et présentant une hybridation dominante du type sp³ (typiquement 60-95% sp³ et 5-40% sp²) ;
• a-C:H : carbone amorphe comprenant une proportion non négligeable d'hydrogène et présentant une hybridation dominante du type sp² (typiquement 60-90% sp² et 10-40% sp³ de la proportion du total qui est constitué de carbone) ; et
• ta-C:H : carbone amorphe tétraédrique comprenant une proportion non négligeable d'hydrogène et présentant une hybridation dominante du type sp³ (typiquement 60-95% sp³ et 10-40% sp² du total du carbone).

Beginning at the tip of the diagram representing hydrogen, which is gaseous at normal temperature and pressure, increasing the proportion of carbon of any type of hybridization, one goes through a strip of polymers (indicated by "Poly") and then we enter the hydrogenated carbon domain. Areas of particular interest for their tribological properties are indicated on the diagram by ovals schematically indicating the respective proportions of hydrogen, sp ³ and sp ² hybridizations, which represent (from left to right):

• aC: amorphous carbon substantially free of hydrogen and having dominant hybridization of the sp ² type (typically 60-90% sp ² and 10-40% sp ³ );
• ta-C: tetrahedral amorphous carbon substantially free of hydrogen and having dominant hybridization of sp ³ type (typically 60-95% sp ³ and 5-40% sp ² );
• aC: H: amorphous carbon comprising a significant proportion of hydrogen and having dominant hybridization of the sp ² type (typically 60-90% sp ² and 10-40% sp ³ of the proportion of the total which consists of carbon); and
• ta-C: H: tetrahedral amorphous carbon comprising a significant proportion of hydrogen and having a dominant hybridization of the sp ³ type (typically 60-95% sp ³ and 10-40% sp ² of the total carbon).

These DLC layers can be deposited by PVD (Physical Vapor Deposition) method, or CVD (Chemical Vapor Deposition), PACVD / PECVD (plasma assisted CVD), or any other technique allowing such a deposit. By varying the parameters during deposition, layers having the proportions of hybridization sp ² -sp ^{3 as} well as the desired proportion of hydrogenation (s) can be deposited, and then determined by current measurements. This is well known in the literature, and therefore should not be described in more detail here.

The inventors have determined that, surprisingly, if a DLC layer is deposited on each of the surfaces of two components of the barrel system 1 which rub against each other, and that these two DLC layers are different from each other. one of the other, the coefficient of friction is significantly reduced. This eliminates any wet lubrication, and also causes a significant reduction in component wear.

• Aucun problème de répartition de la graisse. En effet, la graisse doit être bien répartie sur toutes les surfaces qui sont en contact, et a tendance à fluer de manière indésirable. Plus particulièrement, il existe un effet de décantage, par lequel la graisse a tendance à fluer et se retrouver en bas du barillet, ainsi qu'un phénomène de migration de graisse entre les spires du ressort qui peut les faire coller les unes contre les autres grâce à la tension superficielle de la graisse.
• Montage simplifié, car aucune étape d'application de graisse n'est plus nécessaire.
• Effet lubrificateur dès le début. Par contre, la graisse nécessite un certain temps d'utilisation afin de se répartir de manière homogène, ce qui engendre une phase de rodage au début du fonctionnement de la pièce, et après que la pièce soit laissée inutilisée pendant un laps de temps prolongé.
• Protection des pièces contre les attaques environnementales, car les surfaces revêtues de DLC sont isolées de l'environnement par une couche qui est exempte d'oxygène. L'étape de nickelage communément effectuée dans ce but est simplement remplacée par celle du dépôt de DLC, et par conséquent le nombre d'étapes de fabrication du ressort reste inchangé, et les composants du barillet peuvent être des composants standards à l'exception des revêtements en carbone amorphe.
• Protection contre l'usure entre les spires, si la totalité des surfaces du ressort qui sont soumises à des frottements est revêtue.

In general, dry lubrication using DLC has the following advantages in the context of a barrel system:

• No problem of distribution of fat. Indeed, the grease must be well distributed on all surfaces that are in contact, and has a tendency to flow undesirably. More particularly, there is a decanting effect, whereby the grease has a tendency to flow and end up at the bottom of the barrel, as well as a phenomenon of migration of grease between the turns of the spring which can cause them to stick against each other. thanks to the superficial tension of the grease.
• Simplified installation because no grease application step is no longer necessary.
• Lubricator effect from the beginning. On the other hand, the grease requires a certain time of use in order to distribute itself in a homogeneous manner, which generates a break-in phase at the beginning of the operation of the part, and after the piece is left unused for an extended period of time.
• Protection of parts from environmental attack because DLC-coated surfaces are isolated from the environment by a layer that is free of oxygen. The nickeling step commonly performed for this purpose is simply replaced by that of the DLC deposit, and therefore the number of manufacturing steps of the spring remains unchanged, and the components of the barrel can be standard components with the exception of amorphous carbon coatings.
• Protection against wear between turns if all surfaces of the spring that are subject to friction are coated.

In particular, the figure 3 schematically illustrates a portion of a barrel system 1 according to the invention. In this variant, a first amorphous carbon layer 17 of a first type is deposited on the surface of the flange 15b which comes into contact with the cylindrical inner surface 5a of the barrel of the barrel 5. This cylindrical inner surface 5a is also coated with a second amorphous carbon layer 19 of a second type, different from the first type. This same principle can also be applied to the bung 14 and to the inner end 15a of the spring 15, and / or to the upper and / or lower surfaces of the spring 15, if these surfaces may come into contact with the cover 11 or the drum 5 respectively. In particular, said first layer 17 may be deposited at least two locations, in particular on the surfaces of the two ends 15a, 15b intended to be in contact with the bung 14 and the wall 5a of the drum 5 respectively, said second layer 19 being deposited on the corresponding surfaces of the bung 14 and the wall 5a drum 5.

Typically, these two layers 17, 19 differ in their proportions in sp ² -sp ³ hybridizations of amorphous carbon, while other differences are still possible, particularly in the degree of hydrogenation.

One of the two layers 17, 19 contains, for example, a proportion of sp ² hybridization of between 5% and 40%, preferably between 5% and 20%, more preferably substantially 5, 6 or 7% (more generically C or ta-C: H) and an sp ³ hybridization proportion between 60% and 95%, preferably between 80% and 95%, more preferably substantially 95% (more generically aC or aC: H). The other of the layers 19, 17 has, for example, a proportion of sp ³ hybridization comprised between 5% and 40%, preferably between 25% and 35%, more preferably substantially 30% and a sp ² hybridization ratio included between 60% and 95%, preferably between 65% and 75%, more preferably substantially 70%.

In this case, the layer comprising a major proportion of sp ³ hybridization (for example ta-C or ta-C: H) is preferably the first layer 17 on the spring 15, and that comprising a majority proportion of sp hybridization. ² (for example aC or aC: H) is preferably the second layer 19 on the barrel 3, but the reverse arrangement is also possible.

It is also possible that one of the layers 17, 19 has a hybridization ratio of about 50% sp ² and 50% sp ³ , hydrogenated or not, while the other layer 19, 17 essentially comprises C, ta-C: H, aC or aC: H.

The first layer 17 may advantageously be deposited on the entire surface of the spring 15, including its flange 15b, which simplifies its manufacture and avoids a masking step before deposition of the first layer 17 (see below). This variant is illustrated on the figure 4 , and is the simplest to manufacture. Moreover, if the spring 15 may rub against the cover 11 or the bottom of the drum 5, said second layer 19 may also extend on these surfaces. A second layer 19 may also be deposited on the bung 14.

Even more advantageously, the variant illustrated on the figure 5 provides the first layer not only on the surface of the flange 15a intended to be in contact with the surface 5a of the drum 5, but over the entire surface adjacent thereto, that is to say on the outer surface of the assembly of 15. The opposite surface, that is to say the inner surface of each turn opposite the barrel shaft 7, is coated with a third layer 21 of DLC, a third type different from said first type. This third type may be substantially similar to said second type, or different from the first and second types. Those skilled in the art know how to deposit these two different layers 17, 21, for example by means of successive conventional masking and deposition steps, carried out for example before strapping the spring 15, or alternatively carried out with the supported spring 15. lying down and lying in a template.

In the center of the spring, the bung 14 may comprise a fourth layer of amorphous carbon 23, dissimilar to the third layer 21, which may be for example of a type similar to said first type. Alternatively, in view of the fact that the contact between the spring and the plug 14 is less critical than between the flange 15b and the drum 5, the fourth layer of DLC may be similar to said second type, or may be omitted.

As regards the upper and lower faces of the spring 15, if they are likely to rub against the cover 11 or the bottom of the drum 5, the same considerations as those discussed in connection with the figure 4 also apply here.

The variant of the figure 5 has the advantage that each surface that comes into contact with another surface rubs against a surface having a dissimilar DLC layer, thereby maximizing the friction reducing effects provided by the invention.

For all the variants mentioned above, the layers 17, 19, 21, 23 typically have a thickness between 100 nm and 3 μm, ideally between 250 nm and 950 nm, and are deposited by one of the processes mentioned above. above (PVD, CVD, PACVD, PECVD ...) at a temperature typically between 80 ° C and 220 ° C. These temperatures are sufficiently moderate not to interfere with the quenching of the spring 15.

The advantages conferred by the invention have been demonstrated experimentally. The applicant has submitted two types of barrel systems 1, having their spring 15 and the inner wall 5a of their drum 5 coated according to the variant of FIG. figure 4 of the present invention, to accelerated aging tests corresponding to twenty-eight years of wearing. Two types of barrels 3 were tested: the first barrel 3 had a fixed flange 15b (also called "manual barrel"), while the second barrel 3 had a sliding flange 15b ("automatic barrel"). Measurements and aging were specific for each of them, in order to best represent the actual conditions of use.

These accelerated aging tests have shown that the wear resistance of the barrel systems according to the invention is much greater than that of standard barrels. After the aging phase corresponding to 28 years of use under standard conditions, the barrel systems 1 according to the invention show no reduction in their functional properties. In addition, after the tests, the inner wall 5a of the drum 5 had undergone very moderate wear, despite significant stress during the aging cycles. No material removal or formation of wear particles was observed.

The traditional barrel systems 1, meanwhile, suffered a loss of functionality from five to seven years and therefore require service every two to five years, involving of course a disassembly often preventive movement of the watch. It should also be noted that accelerated aging tests are to the advantage of standard barrel systems because the grease has no time to age, and the high rotational speeds used promote good distribution. The interval between services of the movement is then advantageously increased thanks to the present invention.

Although the invention has been described above in connection with specific embodiments, additional variants are also conceivable without departing from the scope of the invention as defined by the claims. Moreover, the principle of the invention can also be used for other components of a watch movement which are not the subject of the claims, such as for example a finger on a column wheel, the teeth of mobiles, cogs and gears, fork and dowel entrances or coaching fingers.

Claims (12)

System (1) for a timepiece cylinder, said system (1) comprising: - a barrel (3) comprising a barrel shaft (7), a barrel drum (5) coaxial with said shaft (7); - a barrel spring (15) disposed within said barrel (3), said spring (15) being connected by a first end (15a) to said shaft, and connected by a second end (15b) to said barrel by the intermediate of a flange that comprises said second end (15b) of said barrel spring (15), said spring (15) comprising a first layer of amorphous carbon (17) of a first type on at least a part of its surface, characterized in that at least one component (5, 7, 11) of said barrel (3) comprises a second layer of amorphous carbon (19) of a second type, different from said first type, on at least a part of its surface intended to be in contact with said barrel spring (15), said first layer (17) and said second layer (19) being arranged to contact at least a portion of their respective surfaces, and in that said second layer (19) differs from said first layer (17) with respect to the hybridization proportions of the carbon atoms in each of said layers (17, 19). System (1) according to the preceding claim, wherein said first layer (17) is disposed on at least one of: at least a portion of said flange (15a) of said spring (15); at least a part of the turns of said spring (15). System (1) according to at least one of the preceding claims, wherein said second layer (17) is arranged on at least one of: at least a portion of the inner wall (5a) of the drum (5); at least a portion of the flat internal face of said drum (5); - At least a portion of a bung (14) that includes said shaft (7); - At least a portion of a surface of a cover (1) that comprises the barrel (3), said surface facing said spring (15). System (1) according to claims 2 and 3, wherein: said first layer (17) is disposed on said flange (15b) of the spring (15) as well as on the outer surface of the turns of the spring (15); - said second layer (19) is disposed on at least a portion of the inner wall (5a) of the drum (5) and intended to be in contact with said first layer (17); a third layer (21) of amorphous carbon, of a third type different from said first type, is disposed on the inner surface of the turns of the spring (15), said third type preferably being substantially similar to said second type. System (1) according to claim 4, wherein a fourth layer of amorphous carbon (23), of a fourth different type to said third type, is disposed on a bung (14) that includes the shaft (7) and to which the inner end (15a) of said spring is bonded, said fourth type preferably being substantially similar to said first type. The system (1) according to claim 1-5, wherein one of said first layer (17) and said second layer (19) has a higher proportion of sp ³ hybridization carbon atoms than that of the another of said first layer and said second layer (19; 17). The system (1) of claim 6, wherein said first layer (17) has a higher sp ³ hybridization carbon content than said second layer (19; 17). System (1) according to one of claims 6 and 7, wherein the sp ² -sp ³ hybridization proportions of one of said first layer (17) and said second layer (19) are between 5% and 40% of sp ² carbon atoms and between 60% and 95% of sp ³ hybridization carbon atoms, while the proportion of sp ² -sp ³ hybridizations of the other of said first layer (17) and said second layer (19) is between 60% and 90% sp ² hybridization carbon atoms and between 10% and 40% sp ³ carbon atoms. System (1) according to the preceding claim, wherein the proportions of sp ² -sp ³ hybridizations of one of said first layer (17) and said second layer (19) are between 5% and 20% of atoms of hybridization carbon sp ² and between 80% and 95% of sp ³ hybridization carbon atoms, while the proportions of sp ² -sp ³ hybridizations of the other of said first layer (17) and said second layer (19) are between 65% and 75% of sp ² hybridization carbon atoms and between 25% and 35% of covalent sp ³ hybridization hybridization carbon atoms. System (1) according to claim 5 and according to one of claims 6 to 9, wherein the proportions of sp ² -sp ³ hybridizations of one of said third layer (21) and said fourth layer (23) are between 5% and 40% of sp ² carbon atoms and between 60% and 95% of sp ³ hybridization carbon atoms, while the sp ² -sp ³ hybridization proportions of the other of said third layer (21) and said fourth layer (23) are between 60% and 90% sp ² hybridization carbon atoms and between 10% and 40% sp ³ hybridization carbon atoms. System (1) according to the preceding claim, wherein the proportions of sp ² -sp ³ hybridizations of one of said third layer (21) and said fourth layer (23) are between 5% and 40% of atoms of hybridization carbon sp ² and between 60% and 95% of sp ³ hybridization carbon atoms, while the proportions of sp ² -sp ³ hybridizations of the other of said third layer (21) and said fourth layer (23) is between 65% and 75% of sp ² hybridization carbon atoms and between 25% and 35% of sp ³ hybridization carbon atoms. System (1) according to one of the preceding claims, wherein each of said layers (17, 19, 21, 23) has a thickness between 100 nm and 3 microns, preferably between 250 nm and 950 nm.

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