EP2866100B1 - Seal for a clock piece - Google Patents

Description

The present invention relates to a new type of seal for a timepiece, and more particularly to a screw-retained crown comprising such a seal.

In the field of watchmaking, it seeks to seal the boxes as best as possible and preserve their interior from any intrusion of humidity, which can generate fogging and prevent any correct reading of the time. In the longer term, it is also necessary to preserve all internal metal parts, including those constituting movement, premature aging due to oxidation. This need for sealing is even particularly critical for watches intended for immersion use, such as diving watches.

For certain parts comprising moving parts of a watch, such as screwed crowns or pushers, the sealing of the moving parts relative to the fixed parts, as typically tubes integral with the middle part, is guaranteed by means of a or more joints, whose elastic properties, geometric shape and spatial arrangement relative to other parts condition the quality of the seal. The seals are generally made of elastomeric material and of flat and / or toric shape, in the latter case they are generally referred to as an O-ring type seal. Such joints can be mounted directly on the tube, such as those illustrated for example on the crown of the EP1124167 , or inside a bonnet of a crown, such as the O-ring seal of the crown of the international application WO2012 / 168243 which is retained axially by a ring covering the bottom of the hood, commonly called deckring.

A known problem with O-rings relates to their susceptibility to pinching and their propensity to partially wrap around themselves according to the diameter of the torus when they undergo compressive or axial friction forces, which may result in their partial shearing. , or even total, and in any case greatly deteriorate the desired sealing properties. In order to reduce the risk of damage to such joints when they undergo deformation forces, and at the same time to improve their sealing properties, quadrilobe joints have been introduced. Due to the increased number of points of contact between the seal and the contact faces of its housing, the reliability of the seal is increased, and in parallel, thanks to the reduction of the friction forces exerted on each of its points, the forces in torsion are also minimized and therefore robustness and increased service life.

A major advantage of a quadrilobe seal is not to exclusively present the joint plane directly in contact with the sealing surface. The reliability of the sealing is improved the quadrilobe shape also allows to build small tanks of grease or oil (located in the hollows of the seal, ie between the lobes) in the case of a lubricated assembly and thus avoids at the joint premature aging due to lack of lubricant. Nevertheless, quadrilobe joints are relatively expensive because of their complexity of machining due to the particular geometrical shape to achieve. In addition, they have a larger footprint O-rings of the minimum radius of each lobe made in the injection mold.

An object of the present invention is therefore to provide a solution for timepiece joints without the known limitations of O-rings, which is a reliable alternative to quadrilobic joints in terms of performance and in parallel does not generate substantial additional cost of production.

For this purpose, the subject of the invention is a sealed timepiece comprising an overmolded seal, a cover, and a tube, the overmoulded seal being overmolded on an external surface of said tube, the cover being formed by a cover and a cover. an axial skirt covering said tube, a portion of the outer contour of said overmolded seal flush with an inner surface of said axial skirt, said cap being able to assume a plurality of axial positions with respect to said tube, said overmolded seal being axially compressed in at least one of said axial positions, characterized in that the cover comprises a compression ring provided with an oblique surface. A first advantage of the proposed solution is that it significantly improves the sealing properties by removing the joint plane in the area to be sealed, unlike O-rings rings type. Indeed, for the latter the joint plane, materializing the joint between two shells of a mold, is generally constituted by a median plane of the torus whose intersection with the torus is generally of annular section, whose inner diameters and exterior are in contact with bearing surfaces while the surface of the torus is not as smooth and clean in these places as on the rest of its outline.

Another advantage of the proposed solution is that it provides an increased flexibility in terms of room shape on which the overmolding operation can be performed, as well as the shape of the joint itself. Unlike conventional O-rings, the molded seal can be made on any geometrical part, and the vulcanization process to make it a thickness, width or any other dimension wanted if necessary, which allows to move away from the conventional toroidal shape intended only for cylindrical parts.

Yet another advantage of the proposed solution is that it allows a gain in space both radial and axial, the thickness of the seal may be lower than in the case of a reported seal in a groove, and the housing less high.

• la figure 1 montre une vue de dessus d'une couronne vissée, pourvue d'un logo sur la face externe du couvercle de son capot;
• la figure 2 montre une vue en demi-coupe de la couronne orientable de la figure 1, au repos en position dévissée;
• la figure 3 montre une vue en demi-coupe de la couronne orientable de la figure 1 en position vissée;
• la figure 4 est une vue en demi-coupe de la couronne orientable de la figure 1 selon un mode de réalisation préférentiel de l'invention, en position tirée.

Other features and advantages of the present invention will appear in the following description of a preferred embodiment, presented by way of non-limiting example with reference to the accompanying drawings, in which:

• the figure 1 shows a top view of a screwed crown, provided with a logo on the outer face of the lid of its hood;
• the figure 2 shows a half-sectional view of the adjustable crown of the figure 1 at rest in the unscrewed position;
• the figure 3 shows a half-sectional view of the adjustable crown of the figure 1 in screwed position;
• the figure 4 is a half-sectional view of the adjustable crown of the figure 1 according to a preferred embodiment of the invention, in the fired position.

In the preferred embodiment illustrated by all of the following figures, the overmolded seal is disposed on the tube of a screwed crown designated by the general reference 1. According to variants not shown, it could however arrange such an overmolded seal on a piece such as a winding stem, a pusher pin, or any other element constituting a sealed piece intended to be mounted on a timepiece. On the figure 1 , which is a top view of the crown 1, we can distinguish the logo L "Meco" of the plaintiff, arranged on the outer face 113 of the cover 112 of its cover 11. For aesthetic reasons, this logo L is intended for be adjusted in a perfectly horizontal position corresponding preferably to the plane of the middle part of the watch on which is mounted the crown. In this figure we can also distinguish, on the outer periphery of the cover, a toothing D which aims to improve the grip of the crown 1 by the user during its use.

The figure 2 is a sagittal half-sectional view along the axis of rotation AA of the ring 1 which is shown in the unscrewed position commonly called "T1", on a threaded tube 10, intended to be screwed into a middle part of a watch case - not shown - by means of a first thread 101, while a thread 102 cooperates with the thread 21 a central barrel 2 of tubular form, integral with the cover 11. According to an alternative embodiment, the internal thread 102 of the tube 10 could, however, consist of a ^2nd thread and the thread 21 of the central tube 2 may consist of a reciprocally tapping, as for a conventional crown screwed directly to the tube. However, it will be possible to favor an internal threaded crown, such as the proposed tapping 102, to protect the inside of the crown by a seal and thus minimize the risk of fouling and galling.

The cover 11 is formed by a cover 112 and an axial skirt 111, which mutually define a central opening 115 inside the ring forming the screwed element 1 and in which is disposed the end of the threaded tube 10 integral with the middle, but also the central barrel 2. According to the preferred embodiment illustrated, the central threaded barrel 2 consists of an intermediate element between the cover 11 of the crown 1 and the middle part of the watch and a rod (not shown, but conventionally mounted through the tapping 51 in a blind hole at the lower end of the piston 5) interacting with the movement. In the screwed position on the tube 10, illustrated by the figure 3 hereinafter, the orientation of the central barrel 2 is always almost identical with respect to the tube 10, with the difference of the compression level of the overmoulded joint 4. Consequently, the angular orientation of the logo L is also always identical, by transitivity at the middle, in which the latter is also screwed via the first thread 101.

The piston 5 housed inside the central barrel 2 can slide against a spring 3 abuts on a central surface 1141 of the inner face 114 of the cover 112 of the cover 11, and allows in particular to bring out the hood 11 of the middle when unscrewing the crown 1 of the tube 2 during its use for the adjustment of a function (eg a time setting, date adjustment or manual winding of the movement, in different axial positions). The axial stroke of the piston 5 along the axis AA of rotation of the ring 1 is limited by an abutment arranged at the bottom 2. The piston 5 comes into abutment when the ring 1 is unscrewed from the tube 10, as shown in FIG. figure 4 described below.

As can be seen in the preferred embodiment illustrated by the figure 2 , the seal 4 is overmolded on an outer surface of the tube 10, and more particularly on a portion of the tube 10 situated above a shoulder 103 whose upper surface 1031 constitutes a radial bearing surface for the overmolded seal 4. This bearing surface is preferably flat so as to cooperate optimally with a mold during an injection overmolding operation; nevertheless, this surface could also be notched with radial grooves in an alternative way to avoid any torsional detachment of overmolding during compression or relaxation of the compression. The overmolding operation is also facilitated by the fact that the end of the tube 10 above the shoulder 103 is easily accessible, unlike any recessed shape in which the seals are generally arranged. Such an arrangement thus allows productivity gains. According to this preferred embodiment illustrated, the tube 10 also comprises a portion having a projecting profile 104, here in the form of a peripheral bead, which forms attachment surfaces 1041 for the axial retention of the overmolded elastomeric material. This projecting profile 104 is preferably at half height H of the overmolded seal 4, so that the latter is disposed symmetrically on either side of the axial attachment surfaces 1041 and thus has isotropic compression properties. Furthermore, the attachment surfaces 1041 are preferably oblique so as not to have too sharp angles, which would be detrimental to the adhesion of the seal to the tube during the overmolding operation. According to an alternative embodiment, the projecting profile could be replaced by a hollow profile in the form of, for example, a groove of revolution, while still advantageously always having axial attachment surfaces 1041 for the elastomer or any other thermoplastic material and / or thermosetting used to form the molded joint 4. The advantage to use a projecting profile 104 is to minimize the supply of material for the seal therefore also its maximum compression level, that is to say the absolute maximum difference between the shapes of its contour 41 in the compressed position and resting.

According to the preferred embodiment illustrated by the figure 2 , the overmolded seal 4 has a thickness E which is substantially equal to the width of the shoulder 103 of the tube 10, so that the radial space is reduced to the maximum, unlike an O-ring type of seal a part substantially overflows from their homes. According to a preferred embodiment described, the thickness E of the overmolded seal is preferably between 0.15 and 0.25 mm, and the height H of the seal, preferably between 0.3 and 0.4 mm mm. These dimensions are compared to O-ring type seal diameters of about 0.4 mm for crowns of similar size. Therefore, the space saving, calculated in proportion to the section sizes of the overmolded joint 4 with respect to a standard O-ring seal, is at least 15%, and can be up to more than 50%. It is also preferably chosen a height H always greater than the thickness E to minimize the radial size for a given section of the seal. Such radial dimensions are intended to prevent further pinching with the inner wall of the cover 11, that is to say the inner surface 1111 of the axial skirt 111. To further minimize the risk of pinching while ensuring the seal of the ring 1, the overmolded seal 4 comprises dimensions preferably arranged so that a portion of its outer contour 41, or its radial peripheral portion, is flush with the inner surface 1111 of the axial skirt 111. Thus the seal is very little compressed radially and can hardly be pinched between the upper surface 1031 of the shoulder 103, and the inner surface 1111 of the axial skirt 111. In this configuration, the lateral surface 1033 of the shoulder 103, vertical, makes directly facing the inner surface 1111 of the axial skirt 111, also vertical, with a minimum spacing to maintain properties sealing even in this work unscrewed T1 position where the cover 11 of the ring 1 is shifted by a first stroke C1 of about 0.75 millimeters, and at most one millimeter from the screwed position T0 where the seal overmoulded 4 is compressed and therefore the sealing properties of the crown 1 maximum.

On the figure 2 it is also possible to distinguish a first lower surface 1112 planar under the axial skirt 111, and a second lower flat surface 1032 of the shoulder 103. Furthermore, a compression ring 6 having an oblique surface 61 is arranged at the level of the inner face 114 of the hood cover 11, the function of which is explained in the light of the figure 3 described below.

The figure 3 illustrates the same ring 1 according to a preferred embodiment than those of the preceding figures, but this time in its screwed position, that is to say the one in which the cover 11 is in its most proximal position relative to the tube 10 , commonly known as "T0" for a screwed crown. In this position, it can be seen from the shape of its outer contour 41 that the overmolded seal 4 is strongly compressed axially by the compression ring 6, but relatively little radially. The outer contour 4 of the seal follows not only the upper surface of the shoulder 1031, but now also the inner surface 1111 of the axial skirt 111 and the oblique face 61 of the compression ring 6. As on the figure 2 previous, the inner surface 1111 vertical axial skirt 111 faces the side wall 1033 of the shoulder, with a minimum gap the smallest possible, of the order of a few hundredths of a millimeter; however, from now on, the molded joint 4 is compressed so that the first and second lower surfaces 1112, 1032, respectively of the axial skirt 111 and of the shoulder 103 of the tube 10 are almost in line with one another. screwed position of the crown. In practice we try to keep a small offset of the order of 0.1 mm to prevent the crown from exerting strain constraints on the middle in its proximal screwed position and facilitate the gripping of the crown by the user at the beginning of unscrewing. The end of the second internal thread 102 of the tube 10, which also constitutes an axial abutment for the cover 11 of the crown 1, can be similarly determined so as to confine the first lower surface 1112 of the cover 11 of the crown 1 in a position axial as close to the middle as the second lower surface 1032 of the shoulder of the tube 10 when the latter 10 is screwed through its first external thread 101.

As can be seen from the figure 3 , the molded seal 4 is compressed almost exclusively axially and has a minimum remaining height h1 significantly less than the total height H of the overmoulded seal 4 at rest. The maximum height h 2 deduced from the overmolded seal 4 in the compressed position, which is equal to the difference between the total height H and this minimum remaining height h 1, depends inter alia on the orientation of the oblique surface 61 of the clamping ring 6 which according to a variant could come from material with the cover 11. According to the preferred embodiment illustrated, the oblique surface 61 is inclined by about 45 degrees; the more it is inclined vertically, the greater the ratio between the maximum height h2 deduced and the height at rest H of the overmolded seal 4, determining a compression ratio, will be large, especially for molded joints 4 whose section has a height H much higher to the thickness E. Conversely, the compression ratio of the seal will be lower for a sloping surface more horizontally. It may further be noted that according to the preferred embodiment illustrated, the inclination of the oblique surface 61 is identical to that of the upper attachment surface 1041, so that the upper part of the overmolded seal 4 is compressed relatively homogeneous between two parallel flat surfaces. For a given height H of the overmolded joint, the gain in height compactness of screwed crowns using the molded joint of the invention can thus be further improved even more that the maximum height h2 deduced from the overmolded seal 4 will be large. For a molded joint 4 with a height H between 0.3 and 0.4 mm according to the preferred embodiment illustrated, this gain in height, represented by the height h 2 on the figure 3 , is preferably greater than one tenth of a millimeter, which corresponds to a compression ratio h2 / H of more than 25%.

The figure 4 illustrates the screwed crown of the preceding figures but in the pulled position T2, that is to say where the stroke of the barrel 2 relative to the tube 10 is even greater than in position T1. Most references are identical to those of Figures 1 to 3 they will not be explained again in detail; the only major difference between the figure 2 also showing the overmolded seal 4 in uncompressed position relates to the second stroke C2, corresponding to the distance between the first lower surface 1112 of the axial skirt 111 and the second lower surface 1032 of the shoulder 103 is preferably between 1, 5 and 2 millimeters, and is about twice the first race C1. In the pulled position T2, however, the inner surface 1111 of the axial skirt 111 remains in contact with the contour 41 of the overmoulded seal 4 in order to maintain the sealing properties of the crown 1

The material for producing the seal may preferably consist of an elastomer of NBR or HNBR type, and the overmolding operation may be carried out either directly by injection or by compression and vulcanization.

It may be noted that in the context of the present invention, the overmolded seal 4 is overmolded preferably on a crown tube; according to a variant not illustrated, overmolding could however also be performed alternately in a crown head. The choice to favor the tube as a molded object is nevertheless justified by the fact that the overmolding operation is facilitated by a simpler mold construction and access for the injection cannulas. Deburring and dimensional control are also easier than in the case of internal overmolding.

Claims (6)

1. Water resistant timepiece comprising an overmoulded gasket (4) and a cover (11), characterized in that the timepiece comprises a tube (10), in that the overmoulded gasket (4) is overmoulded on an outer surface of said tube (10), in that the cover (11) is formed of a lid (112) and of an axial skirt (111) covering said tube (10), in that one portion of the outer contour (41) of said overmoulded gasket (4) is flush with an inner surface (1111) of said axial skirt (111), said cover (11) being capable of taking several axial positions (TO, T1, T2) with respect to said tube (10), said overmoulded gasket (4) being axially compressed in at least one of said axial positions, and in that the cover (11) comprises a compression ring (6) provided with an oblique surface (61).
2. Water resistant timepiece according to claim 1, characterized in that said tube (10) comprises a shoulder (103) forming a radial support surface (1031) for said overmoulded gasket (4).
3. Water resistant timepiece according to any of the preceding claims, characterized in that said tube (10) comprises a protruding portion (104) forming axial attachment surfaces (1041) for said overmoulded gasket (4).
4. Water resistant timepiece according to claim 3, characterized in that said overmoulded gasket (4) is symmetrically disposed on either side of said attachment surfaces (1041).
5. Water resistant timepiece according to claim 2, characterized in that the thickness (E) of said overmoulded gasket (4) is substantially equal to the width of the shoulder (103) of said tube (10).
6. Timepiece according to claim 1, characterized in that said axial skirt (111) comprises a first flat lower surface (1112) and in that said tube (10) comprises a shoulder (103) provided with a second flat lower surface (1032), characterized in that said overmoulded gasket (4) is capable of being compressed in a first axial position (TO) such that said first and second lower surfaces (1112, 1032) are virtually in the extension of each other.

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