Horology: time measuring systems or devices – Cases – With bezel or crystal details
Reexamination Certificate
2000-02-29
2001-03-27
Miska, Vit (Department: 2859)
Horology: time measuring systems or devices
Cases
With bezel or crystal details
Reexamination Certificate
active
06206563
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device for the leakproof fastening of a watch glass to a watch case, comprising an annular seal of cylindrical general shape, made of a compressible material and having an inner annular projection at the upper end of this annular seal, an annular groove made on that edge of the watch glass into which this annular projection is engaged, an outer lateral surface made on the upper part of the housing in order to receive the lower part of the inner face of said annular seal, the base of which comes into abutment against a bearing surface, and a bezel fitted around said seal, at the same time compressing the latter radially.
Devices are already known for the leakproof fastening of a glass consisting of hard material, such as toughened glass or sapphire, in which the glass consisting of hard material is fastened in a ring produced from a material which is soft in relation to the watch glass and also in relation to the metal of the case to which it is to be fastened. This ring usually consists of organic glass, such as Plexiglass.
DESCRIPTION OF THE PRIOR ART
A fastening device of this type is described in CH 519 193, in which the watch glass is accommodated in a ring consisting of organic glass, the entire assembly subsequently being introduced by mounting into a receptacle of a bezel housing, the deformations resulting from the mounting operation being absorbed by the ring consisting of organic glass which also ensures the leakproofing of the fastening. A false bezel may be fastened to the bezel housing in order to conceal the fastening ring of the watch glass. In a variant, the fastening ring is accommodated in an annular groove made in the edge of the watch glass, so as not to project from the periphery of the latter and thus not be visible.
Such a fastening device is necessary for the annular seal surrounding the watch glass to be subjected to stress before this assembly is fastened in an orifice of the housing. The removal of this assembly presents serious problems, since the prestressed seal is entirely embedded in the housing and the glass of sapphire or toughened-glass type cannot be deformed.
CH 583 438 proposed a solution which does not have the abovementioned disadvantages and in which the annular seal made of relatively soft glass, which surrounds the watch glass, is engaged around a lateral surface made on the upper end of the housing, around the raised portion, and is compressed radially against this lateral surface by the bezel mounted around this seal. In a preferred embodiment, not described in this patent, the bezel extends over the entire height of the annular seal, so that the upper part of this seal is compressed between the bezel and the watch glass and so that the lower part of this seal is compressed between this bezel and the lateral surface of the housing on which it is engaged.
Although this fastening method has proved successful for many years, particularly with regards leakproofing, it became clear that its design was capable of being improved even further in many respects.
Thus, in the abovementioned fastening system, only the frictional force makes it possible to ensure that the annular seal is fastened to the lateral surface of the housing, so that the seal must have sufficient rigidity, giving rise to pronounced stresses on the other parts, particularly giving rise to a torque tending to deform the raised portion and the bezel.
The same surface of the bezel serves for clamping the seal around the watch glass and around the lateral surface of the housing. In view of the many manufacturing tolerances in the various elements involved in this fastening, the force necessary for removing the bezel may vary in a ratio of 1 to 4. In view of the differences in the frictional forces occurring as a result of these tolerance variations, the position of the bezel after mounting may change slightly from one piece to another, thus having effects on the compression of the annular seal.
During the mounting of the bezel, the seal undergoes deformations in the region of the watch glass which are greater than those determined by leakproofing. If this seal is clamped firmly, there is a risk that it will form a bead which is interposed between the housing and the bezel and prevents the latter from being laid against the housing. It is also possible, in the event of a sharp compression of the annular seal, that the latter is deformed into the space provided between the watch glass and the housing.
As a consequence of the design of the assembly operation, in which, in the assembled position, the bezel is held solely by friction around a piece consisting of compressible material, the bezel remains subject to a force tending to cause it to rise.
Finally, the injection points can be located only in a visible zone or in a contact zone and are therefore annoying in both cases.
BRIEF SUMMARY OF THE INVENTION
The object of the present invention is partly to overcome the abovementioned disadvantages.
To achieve this, the subject of this invention is a device for the leakproof fastening of a watch glass to a watch case according to claim
1
.
One of the essential advantages of the present invention is due to the fact that the base of the annular seal is retained on the housing by anchoring and no longer by friction. Consequently, the extreme values of the force necessary for removing the bezel come within a somewhat limited range, in spite of the disparity of the clamping values inherent in the manufacturing tolerances of the various elements.
Another great advantage is due to the fact that the annular seal is no longer radially compressed uniformly over its entire height, but that two separate compression zones are formed, one in the region of the watch glass and the other in the region of the fitting surface, adjacent to the upper edge of the housing. Thus, during the mounting of the bezel, its base does not compress the upper part of the seal, thus avoiding the risk of formation of a bead which comes into place between the bezel and the housing.
That part of the annular seal which is located between the lower face of the watch glass and the upper edge of the housing is not compressed, or compressed very little, radially, thus avoiding the risk of being deformed into the free space separating the watch glass from the housing. The radial compressions induced in the two clamping zones are not necessarily the same, but may be adapted to requirements independently in each zone. Since the hold of the assembled elements is not attributable solely to the frictional forces, it is then possible to use a seal consisting of a less rigid material, thus making it possible to reduce the stresses exerted on the other elements and, in particular, on the raised portion.
Contrary to the seal of the fastening device of the prior art, in the present invention, when the seal is injected, the injection points of the seal may be arranged, particularly with regard to opaque seals, in that portion of its outer face which is located between the bulge of the base of the seal and the part of smallest diameter of the inner face of the bezel. After mounting, this portion is, in fact, concealed by the bezel and also forms a non-functional zone of the seal, since said portion is not in contact with any surface of the bezel.
It can be seen that, by preserving the same general principle for the leakproof fastening of the watch glass as that known from the prior art, the present invention makes it possible to afford substantial improvements which are appreciable, in particular, during the assembly operations and also in terms of maintenance, since demounting is thereby made easier by a narrower dispersion of the values of the forces for removing the bezel, without any impairment in leakproofing efficiency, on the contrary.
REFERENCES:
patent: 2854815 (1958-10-01), Piquerez
patent: 4456388 (1984-06-01), Matsumoto
patent: 4668101 (1987-05-01), Wuthrich
patent: 583 438 (1976-12-01), None
patent: 653 844 (1986-01-01), None
patent: 28 17 770 (1978-11-01), None
Dombre Christian
Passaquin William
Henderson & Sturm LLP
Miska Vit
Montres Rolex S.A.
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