CH714145B1 - Gasket for cover part. - Google Patents

Abstract

The present invention relates to use in a trim piece (2) comprising a fixed element (6) intended to be fixed to a watch case and a movable mounted element (7) relative to the fixed element (6). ); of a seal (1) disposed between the two elements (6,7), characterized in that said seal (1) has been subjected on at least part of its surface to an ion implantation treatment in order to reduce the coefficient friction between the seal (1) and the movable mounted element (7) or between the seal (1) and the fixed element (6). The present invention also relates to the cover part (2) provided with said seal (1) and to the watch provided with the cover part (2). The invention aims to reduce an increase in the friction of the seal (1) following the aging or disappearance of a lubricant.

Description

Object of the invention

The present invention relates to the field of seals used in trim parts in watchmaking.

Technological background

[0002] The trim parts such as valves, correctors, pushers or even crowns are provided with gaskets making it possible to ensure the seal between the outside and the inside of the watch case. These seals are often made of an NBR or HNBR elastomer material lubricated under the conditions of delivery in order to limit their friction in use. Over time, following aging or even in contact with cleaning products or water, the lubricant tries to disappear, leading to an increase in the coefficient of friction and, thereby, a change in the behavior of the actuator. An increase of 10 to 70% in the coefficient of friction between the seal and the corrector tube is thus observed, which may hinder the return of the corrector head to its rest position after stress. Similarly, the pressure required to actuate the pusher or the torque of the crown may be increased as a result of the increased friction. In the case of valves, lack of use can lead to a sticking of the seal on the valve stem resulting in an increase in the opening pressure of the valve with pressure values that can increase from 0.5 to 6.0 bar helium. Furthermore, in the case of crowns and pushrods, lubrication is carried out at the end of the production process, i.e. during assembly, particles are liable to stick to the lubricant layer causing a loss of sealing of the product. Washing is not an option because it would remove the lubricant and re-lubrication does not give a reliable result.

[0003] In all cases, the deterioration of the lubricating layer of the seal leads to a behavior which varies over time and therefore is unreliable for the actuator. To overcome these drawbacks, making a seal with materials having intrinsic lubricating properties such as Teflon (PTFE), molybdenum disulphide or even graphite may prove to be advantageous. However, these materials are expensive and difficult to manufacture in small dimensions for the watch industry.

Summary of the invention

[0004] To remedy the aforementioned disadvantages, the main object of the present invention is to provide a seal exhibiting in use a low coefficient of friction which is stable over time without having to resort to a layer of lubricant or a material having intrinsic lubricating properties.

[0005] For this purpose, the present invention proposes to use within the covering part a seal which has undergone an ion implantation treatment on its extreme surface.

[0006] Thanks to the ion implantation treatment, the coefficient of friction is maintained at a substantially constant value over the life of the product with, as a corollary, a stable and reliable behavior of the actuator over time.

[0007] Compared to an unlubricated seal made with the same base material, the coefficient of friction of the seal subjected to the ion implantation treatment alone is reduced by several tens of percent with values reduced from 10 to 70% depending on the ion dose.

[0008] The conditions for carrying out this treatment, in particular working under high vacuum and at low temperature, make it a particularly clean technique suitable for a watchmaking application. Another advantage of this treatment is that it does not lead to any geometric modification of the joint during the treatment. Likewise, the proposed treatment is not a coating and therefore does not cause debris formation or peeling problems during use.

[0009] Other advantages will emerge from the characteristics expressed in the claims, from the detailed description of the invention illustrated below with the aid of the appended drawings given by way of non-limiting examples.

Brief description of the figures

Figures 1 to 4 respectively show half-section views of a corrector, a pusher, a crown and a valve provided with a seal having undergone an ion implantation treatment on the extreme surface according to the invention. FIG. 5 schematically represents a partial view of a seal according to the invention comprising a layer of ions implanted on the extreme surface.

Detailed description of the invention

The present invention relates to thermoplastic or elastomeric gaskets, in particular made of butadiene-acrylonitrile (NBR) and hydrogenated butadiene-acrylonitrile (HBNR), intended to be used in a timepiece trim part to ensure its sealing. The seal can take several forms. It can be toric with an oval or circular section, flat, axial or with a lip.

According to the invention, the seal having the final dimensions required for the application is subjected before assembly within the trim part to a treatment of its extreme surface allowing in use to reduce its coefficient of friction and avoid the problems of sticking the joint. For this purpose, the seal is subjected to an ion implantation process which consists in bombarding in a vacuum chamber (<10 <-5> mb) ions on the surface of a material with high energy. Carried out at a temperature below 100 ° C, this treatment modifies the structure of the material to a depth of less than 15 µm, which induces a modification of the surface properties.

The choice of ions relates to ions resulting from the ionization of gases such as for example N2, Ar, O2, He, etc. or their mixture. For the application targeted in the present invention, the choice is preferably made on the ions resulting from the N2. The ions are accelerated with an energy between 25 and 200 keV and preferably between 25 and 100 keV for NBR and HNBR seals. The ion dose is preferably between 10 <13> and 10 <16> ions / cm <2> but can range up to 10 <17> ions / cm <2> if more dense filling is desired. The implantation depth is typically between 5 and 10 μm.

The seal 1 according to the invention can be used in a corrector 2, a pusher 3, a crown 4 or even a helium valve 5 as shown respectively in Figures 1 to 4. Conventionally, the seal 1 is arranged between an element 6 intended to be mounted fixed relative to the watch case, such as a tube, and an actuatable element 7 movable relative to the fixed element, such as a rod for the valve 5 and the pusher 3 or a head for the corrector 2 and the crown 4. Depending on the assembly of the seal, the friction can in use be exerted between the seal 1 and the movable element 7 (Figures 2 to 4), or between the seal 1 and the fixed element 6 (figure 1). According to the invention, ion implantation can be carried out over the entire surface of the seal or selectively over the portion of the surface which is subjected to friction in use.

FIG. 5 schematically illustrates with the aid of a partial view a seal 1 according to the invention comprising a layer of ions 8 implanted on the surface of the base material 9.

[0016] Particularly preferably, the seal is only subjected to this ion implantation treatment without resorting to a layer of lubricant. However, the present invention does not exclude combining the ion implantation treatment with an additional layer of lubricant Legend (1) Seal (2) Corrector (3) Tappet (4) Crown (5) Helium valve (6) Element fixed with respect to the watch case, such as the tube (7) Movable element with respect to the watch case, such as the push button or the rod (8) Layer with ion implantation under the surface of the base material (9 ) Base material

Claims (15)

1. Use in a covering part (2,3,4,5) comprising a fixed element (6) intended to be fixed to a watch case and a movable mounted element (7) relative to the fixed element ( 6), of a seal (1) arranged between the two elements (6,7), characterized in that said seal (1) has been subjected on at least part of its surface to an ion implantation treatment in order to reduce the coefficient of friction between the seal (1) and the movable mounted element (7) or between the seal (1) and the fixed element (6). 2. Use according to claim 1, characterized in that the seal (1) is made of a thermoplastic or elastomer material. 3. Use according to claim 1 or 2, characterized in that the seal (1) is made of butadiene-acrylonitrile or hydrogenated butadiene-acrylonitrile. 4. Use according to any one of the preceding claims, characterized in that said seal (1) disposed between the two elements (6,7) is devoid of a layer of lubricant. 5. Use according to any one of the preceding claims, characterized in that the seal (1) is an O-ring, a flat seal, an axial seal or a lip seal. 6. Use according to any one of the preceding claims, characterized in that the ions are implanted with a dose of between 10 <13> and 10 <17> ions / cm <2>, and preferably between 10 <14 > and 10 <16> ions / cm <2>. 7. Use according to any one of the preceding claims, characterized in that the ions resulting from the ionization of gas or of a mixture of gases, preferably of N2, are implanted. 8. Use according to any one of the preceding claims, characterized in that the ion implantation treatment is carried out with an acceleration energy of between 25 and 200 keV. 9. Use according to any one of claims 3 to 8, characterized in that the ion implantation treatment is carried out with an acceleration energy of between 25 and 100 keV for a seal (1) made of butadiene-acrylonitrile or into hydrogenated butadiene-acrylonitrile. 10. Use according to any one of the preceding claims, characterized in that the ion implantation treatment is carried out over the entire surface of the seal (1). 11. Use according to any one of claims 1 to 9, characterized in that the ion implantation treatment is only carried out on the surface of the seal (1) subjected to friction. 12. Use according to any one of the preceding claims, characterized in that the treatment of the seal was chosen to reduce the coefficient of friction from 10 to 70% compared to an identical seal that has not undergone implantation treatment. ionic. 13. Trim part, in particular a corrector (2), a pusher (3), a valve (5) or a crown (4), characterized in that it comprises a seal (1) comprising at least one part on its surface a layer (8) of implanted ions. 14. Dressing part according to claim 13, characterized in that the layer (8) of implanted ions has a thickness between 5 and 15 microns and, preferably, between 5 and 10 microns. 15. Watch comprising the covering part according to claim 13 or 14.