The present invention relates to a removable oscillating weight bearing for automatic mechanical clockwork wristwatch, whose axial play can be adjusted during its assembly on the base movement, this by the judicious choice of a component for adjusting the sloshing of the oscillating assembly.
Figs. 1, 2 and 3 represent by way of example an oscillating ball bearing mass system frequently used by the watch industry. Fig. 1 is a perspective view, figs. 2 and 3 are sections of different scales. These drawings make it possible to see the outer mass segment 1 generally made of high density material fixed to the mass support 2 itself riveted to the toothed ring 4 of the ball bearing 3. The said ring transmitting the circular motion induced by the movements of the oscillating assembly to the gearing of the automatic winding mechanism.
This solution is difficult, because it has many disadvantages due to its reduced dimensions, we will cite non-exhaustive ways that its operation will be correct as soon as: all components will be of optimal quality; the cleanliness, even the lubrication of the bearing will be correct; ball rolling D due to the manufacturing tolerances of each of the components are within an acceptable range.
To overcome the drawbacks mentioned above the patent CH 485 257 proposes, according to its edition FR 1 593 271 a solution excluding the use of a ball bearing. This patent claims a pivoting device for oscillating weight of a self-winding watch, comprising, on the one hand, a flat ring, and, on the other hand, a cylindrical surface on which this ring slides, as well as two annular surfaces. planes directed towards each other, and maintaining said ring in a determined axial position, characterized in that the flat ring, which constitutes the mobile part of the device, is integral with the oscillating mass, and in that said surface cylindrical, and the two annular surfaces forming part of the fixed bearing, are respectively located on three other flat rings,
superimposed and forcibly engaged on the same sleeve. This patent also claims that the three fixed rings are trapped between two shoulders respectively forming part of a frame member and a removable piece which can be separated from the frame with the oscillating mass.
The proposal cited patent is interesting since it solves a lot of the disadvantages of the ball bearing. Its description states in particular that one of the main aims of the invention is to improve the pivoting devices so that they can be removed en bloc with the mass during disassembly of the latter.
If at the time of its filing, this form of execution perfectly matched the needs of the watch industry, especially in terms of cost and ease of production, nowadays it is imperative to be able to dismount a bearing oscillating mass. Indeed, currently the oscillating masses are generally made in high value materials such as gold or platinum and are enriched by expensive decorations even encrusted with precious stones. It will therefore be understood that it is advantageous to be able to disassemble the bearings of such oscillating masses in order to exchange one or the other of the defective components and in fact recover the part made of noble materials or to adjust correctly the sloshing D of the oscillating assembly.
It will also be understood the need to have bearings for high performance oscillating masses in the sense that it is necessary to compensate for the fact that, nowadays, the holders of automatic watches have a lifestyle which on average induces less movements to the oscillating weight than in the past.
We will also mention the patent CH 347 138 which advocates an assembly using a stone driven on a range of a non-movable central cap, stone outside which directly pivots the oscillating mass. The axial fretting of this oscillating mass is here controlled directly by the machining height of the central span of the cap on which the stone is driven.
It will be understood from reading this document that this solution is not able to ensure optimum performance because the axial friction is between metal components. Furthermore, it will also be understood that it does not provide precise control of the sloshing D of the oscillating assembly, this in that the axial play of this bearing is a function of a machining whose height is generally inaccurate.
The present invention relates to a removable oscillating weight bearing for automatic mechanical clockwork wristwatch, the axial play of which influences the sloshing of the oscillating assembly, may in particular be adjusted during its assembly by the judicious choice of a component.
Figs. 4 and 5 represent a bearing of oscillating mass for which the central axis 5 is driven in the support bridge 6, on this axis 5 are free fit the two flanges 7 and 8, knowing that they are kept separated by a ring 9 also free fit on the 5 axis; between the flanges 7 and 8 pivots freely around the ring 9 the oscillating mass assembly consisting of a ruby ring 10 driven into the toothed ring 4 on which the ground support 2 is riveted.
The screw 11 maintains the integral with the axis 5 and the support bridge 6. Just remove the screw 11 to release the elements of the bearing and thus allow its maintenance. The spacing between the two flanges 7 and 8, being determined by the height of the ring 9, a judicious choice of the latter during assembly, will accurately define the play of the ruby ring 10 between the flanges 7 and 8 , the sloshing D of the oscillating assembly will accordingly be adjusted.
To ensure the best possible yield the flanges 7 and 8 are made of hardened steel or other materials may present in combination with the ruby an optimum slip coefficient. It will be noted, according to FIG. 6, that the flanges 7 and 8 each have concentric recesses o and at their peripheries notches q of free forms such that the pads p thus formed are as small as possible to minimize the areas in contact with the ruby and thus promote performance. It will also be noted that the pads p and the central ring n flanges 7 and 8 will be ground and polished simultaneously so that they are strictly in the same plane.
So that the sloshing D of the oscillating assembly is acceptable, it is appropriate that the radius r on which are located the pads p is sufficient. In practice we can admit that this radius must be between 18 and 25% of the outer radius of the oscillating mass. Moreover, it should be noted that the chase of the ruby 10 in the toothed ring 4 is not axially limited, which has the advantage of allowing the adjustment of the safety margin S between the mass support 2 and the bridge. support 6 according to the decorations of variable heights made on the latter.