Patent Application
20080084793
Other advantages and characteristics of the invention will emerge from the following description, rendered with reference to the appended drawing, in which
A preferred embodiment will be described as one example of a way to practice the invention, but its scope is not limited to this embodiment.
The movement represented in the drawing comprises a casing composed of a bottom plate 10, barrel bridges 12 and train bridges 14, as well as two tourbillion plates 16 and 18. The bottom plate 10 and the bridges 12 and 14 are made of brass or gold, whereas the plates 16 and 18 are made of sapphire or any other transparent material.
A barrel 20 is rotatably mounted on the casing. It is loaded by means (not shown) which are well known to the person skilled in the art and which are described, in particular, in the aforementioned work entitled “Théorie d'horlogerie”.
The barrel drives a work train, the last mobile 22 of which performs one revolution a minute. This mobile 22 can bear a seconds hand.
A tourbillion 24 is pivotably mounted between the plates 16 and 18. It comprises a cage 26, two pivots 28 and 30 disposed on either side of the cage and engaged in bearings 16a and 18a belonging to the plates 16 and 18, defining a pivot axis AA of the cage 26.
A balance wheel 32, an escape mobile 34 comprising a wheel 34a and a pinion 34b, and a pallet fork 36 are pivotably mounted on the cage 26.
The cage 26 is provided with a cage wheel 38 composed of a transparent annular platelet 38a, the circumference of which bears a metal ring 38b provided, on its periphery, with a toothing 38c meshing with the mobile 22. As a variant, the toothing 38c could also be cut directly in the platelet 38a.
The plate 18 bears a fixed wheel 40 arranged such that it meshes with the pinion 36b.
The diameter d26 of the cage 26 and the diameter d40 of the fixed wheel 40 are markedly less than the external diameter d38a of the platelet 38a. Since, moreover, the plates 16 and 18 are made of transparent material; an annular portion 42 exists around the cage 26, in which no opaque or visible part is found. Moreover, the plates 16 and 18, as well as the platelet 38a of the wheel 38, comprise no visible edge in the cylindrical portion 42. They cannot, therefore, be seen and the sought-after mysterious effect is achieved.
In the construction represented in the drawing, the cage of the tourbillion performs one revolution every two minutes. Naturally, the number of teeth can be adjusted such that the cycle of the tourbillion is different. It is worth pointing out, however, that the use of a cage wheel responsible for driving the cage increases its moment of inertia. It is hence preferable to have a relatively long rotation cycle to avoid overloading the movement.
Advantageously, this movement is disposed in a sheath defining an opening through which the tourbillion is visible and the circumference of which fits on the outer surface of the cylindrical portion such that the visible parts surrounding the tourbillion are masked.
Naturally, the movement such as described can form the subject of numerous variants, without, for all that, departing from the scope of the invention.
It is thus possible to use a floating tourbillion, that is to say one which pivots only on one of its sides. This solution is, nevertheless, only of minor interest, since the pivot means are virtually not visible. The cage wheel could form an integral part of the cage, the transparent platelet 38a being in this case constituted by a washer, the periphery of which forms the toothing 38c and on which are fixed bridges responsible for pivoting the escape mobile 34, the pallet fork 36 and the balance wheel 32.
It is thus possible to make the whole of the bottom plate and all of the bridges out of transparent material. Such a solution has the drawback, however, of reducing the mysterious effect.
Insofar as the plates 16 and 18 are made of sapphire, it is possible to realize the pivotings of the cage right there. It is also possible to add some stones in holes made for this purpose.
The transparent material may be natural or synthetic material. One example is corundum, which is aluminum oxide, or Al2 O3. A particular species may be sapphire, also known as colorless sapphire. Other transparent, colorless materials include topaz or zircon. The transparent material which is used is advantageously sapphire. It is also possible, however, to use quartz, glass, or even plastics material.
It is equally possible to fix the fixed wheel 40 onto a supplementary transparent plate, likewise fixed to the casing, and more particularly to the bottom plate 10.
This plate would in this case be breached to allow the passage of the shaft of the cage 26.
While a preferred embodiment has been described, the invention is not limited to the preferred embodiment disclosed. Numerous variations and modifications may be made without departing from the spirit and scope of the invention, which is defined by the following claims.
