Patent Application
20120087214
The invention relates to an oscillating body, a mechanical oscillating system and to a watch with several mass weights arranged at regular angle distances around an oscillating body middle axis that respectively can rotate or swivel on the oscillating body on an axis parallel to the oscillating body axis and have a mass center of gravity that is radially offset to this axis.
Oscillating bodies for mechanical oscillating systems of watches, especially wristwatches, are known in different embodiments and they generally have the shape of a wheel or spoked wheel. To adjust the dynamic mass moment of inertia of the oscillating body and therefore the frequency of the oscillating system and the precision of the watch, mass weights are provided in the outer area of the oscillating body, the mass center of gravity of which is adjustable radially or approximately radially to the axis of the oscillating body.
It has been shown that the temperature behavior of a mechanical oscillating system can be improved very decisively in that, when a spiral spring made of silicon (mono or polycrystalline silicon) with an oxidic surface coating, for example, with a coating of silicon oxide, is used, the oscillating body is manufactured from molybdenum or a molybdenum alloy, in which case a certain disadvantage of this material consists in that fact that it is relatively difficult to machine or work with.
It is an object of the invention to present an oscillating body for mechanical oscillating systems of wristwatches that facilitates simplified manufacturing while maintaining a compact design and high stability, especially with high temperature stability.
Preferably, the oscillating body according to the invention is made of a metal material with a density greater than 10 kg/m3 and a linear expansion coefficient smaller than 7×10−3 and a Mohs hardness greater than 5, while the mass weights are manufactured from a material with a high density, for example of gold or brass.
The term “essentially” as used in the invention means deviations from the exact value by +/−10%, preferably by +/−5% and/or deviations in the form of changes that are insignificant for the function.
Further embodiments, advantages and applications of the invention are also disclosed in the following description of exemplary embodiments and the drawings. All characteristics described and/or pictorially represented, alone or in any combination, are subject matter of the invention, regardless of their being summarized or referenced in the claims. The content of the claims is also an integral part of the description.
The invention is described in more detail below based on exemplary embodiments, in which:
In the drawings, a wheel-shaped oscillating body 1 of a mechanical oscillating system (balance wheel) for wristwatches is shown. The oscillating body 1 is manufactured from a stable material, for example, a metal material, preferably of molybdenum, as one piece comprising an outer section 2 concentrically enclosing the axis AS of the oscillating body 1, comprising an inner, hub-shaped section 3 and comprising four spoke-shaped ribs 4 extending radially toward axis AS and connecting the inner section 3 with the outer section 2. The section 3 is provided with an opening 5 that is axially congruent with the axis AS and serves to fasten the oscillating body 1 to a shaft, not depicted.
On the inner side of the outer section 2, identically formed mass weights 6 are distributed at even angle distances around the axis of the oscillating body respectively as a circular disk-shaped pre-formed body 7 with a circular arc-shaped groove 8 enclosing an axis AM of the respective pre-formed body 7 on an angle area smaller than 360°, i.e. in the depicted embodiment on an angle area of 180° or essentially 180°, which (groove) extends from the top side of the pre-formed body 7 to its bottom side. Due to the groove 8, the mass weights 6 have a mass center of gravity that is radially offset to the axis AM.
In assembled state, the mass weights 6, or their pre-formed bodies 7, are oriented with their axis AM parallel to the axis AS of the oscillating body 1. For mounting of the mass weights 6, which are arranged in the middle between two ribs, the outer circular ring-shaped section is designed on the inside as one piece with tab-shaped sections or tabs 9, which extend from the inside of the section 2 radially in the direction of the section 3 or the axis AS. In the area of the free end, the tabs 9 are provided with a closed bore hole 10, whose axis is oriented parallel to the axis AS. The distance of the bore holes 10 from the inner surface of the section 2 is approximately the same or slightly larger than half the diameter of the circular disk-shaped mass weights 6 or pre-formed bodies 7. All bore holes are at the same distance from the axis AS. A formed-on projection 11, which has the same outer diameter as the inner diameter of the bore hole 10, and which is cylindrical in shape on the outer surface and axially congruent with the axis AM and protrudes over the bottom side of the pre-formed body 7, engages into each bore hole 10. Each projection is provided with a bore hole 12, which is open on the face of the projection 11 facing away from the pre-formed body 7 and extends approximately into the transition area between the pre-formed body 7 and the projection 11.
By peening of the projection 11, the mass weight 6 is held on that projection 11 at the corresponding tab 9, so that the pre-formed body 7 bears with its face comprising the projection 11 and enclosing said projection against the top side of the projection 9 and with its top face facing away from the projection 11 does not protrude or protrudes only slightly, for example, with only 0 to 3% of its total axial height, over the plane of the top side of the oscillating body 1.
For the peening, each bore hole 10 is provided on the bottom side of the tab 9 facing away from the pre-formed body 7 with a phase or with a section that enlarges conically toward said bottom side, into which the projection 11 is permanently deformed radially to the axis AM so that said deformed section of the projection 11 is flush with the plane of the bottom side of the respective tab 9, i.e. it does not protrude over said bottom side. Other types of peening or fastening of the mass weights 6 to the tabs 9 are possible, for example, by permanent deformation of the respective projection 11 to form a bead overlapping the edge of the bore hole 10 on the bottom side of the respective tab 9. In any case, the peening of the mass weights 6 is effected so that they are not held reliably on the oscillating body 1, but rather can rotate on their axis AM through application of a torque for adjusting the oscillating body 1 or for setting the mass moment of inertia of said oscillating body and the respective adjustment is reliably ensured by the frictional forces acting between the tabs 9 and the mass weights 6. The bottom side of each tab 9 lies in a common plane with the bottom side of the oscillating body 1 or with the bottom side of the outer circular ring-shaped section 2.
The material used for the oscillating body 1 is a metal material with a density greater than 10 kg/m3, a thermal expansion coefficient of less than 7×10−6 and a Mohs hardness greater than 5. The thermal expansion coefficient is the linear expansion coefficient or the elongation of a length unit at a temperature increase of 1° C. in the temperature range between 0 and 100° C.
The high density produces the required mass weight and mass moment of inertia for the oscillating body 1. The high hardness ensures that the mass weights 6 after peening are held reliably on the oscillating body 1 and nevertheless that adjustment of the dynamic mass moment of inertia of the oscillating body 1 by rotating or swiveling the mass weights 6 around their axis AM is possible. The reduced thermal expansion coefficient results in high thermal accuracy of the oscillating system and therefore high accuracy of the respective wristwatch also in case of changing temperatures.
Suitable materials for the oscillating body 1 are therefore for example tungsten, molybdenum, niobium, hafnium or alloys with a high content of these metals, preferably tungsten/copper alloys with a tungsten/copper ratio of 80/20 or essentially 80/20.
The mass weights 6 are made of a material with a high density so that the mass weights 6 can be manufactured with relatively small dimensions, for example, so that the diameter of the pre-formed body 7 is approximately 1.2 units, the axial height of the pre-formed body 7 is approximately 0.35 units, the diameter of the projection 11 is approximately 0.4 units and the axial length of the projection 11 is approximately 0.2 units, where a unit is 1 mm. In the depicted embodiment, the maximum diameter of the mass weights 6 is approximately 10 to 12% of the total diameter of the oscillating body 1.
In one embodiment of the invention, the oscillating body 1 is made of copper-beryllium and the mass weights 6 are made of stainless steel.
An essential advantage of the oscillating system 1 consists in the fact that the oscillating body 1 has a relatively simple shape, which despite the high hardness of the material used enables simplified production. Due to the arrangement of the mass weights 6 within the outer ring-shaped section 2, practically no space for other components of the mechanical oscillating system or of the mechanical clockwork is lost due to the mass weights 6. Since the mass weights 6 can rotate or swivel on their axes AM parallel to the axis AS for adjustment of the dynamic mass moment of inertia of said oscillating body, the possibility of simplified adjustment is given, in which the grooves 8 can be used at the same time as surfaces for placing a tool used for adjustment.
The invention was described above based on an exemplary embodiment. It goes without saying that numerous modifications and variations are possible without abandoning the underlying inventive idea upon which the invention is based.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2010 033 668.8 | Aug 2010 | DE | national |
| 10 2010 049 210.8 | Oct 2010 | DE | national |
