Horology: time measuring systems or devices – Astronomical – With sun – earth – and moon display
Patent
1986-11-05
1987-12-08
Miska, Vit W.
Horology: time measuring systems or devices
Astronomical
With sun, earth, and moon display
G04B 1926
Patent
active
047115831
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an astronomical watch by means of which astronomical magnitudes may be read directly through the intermediary of indicators moving over a dial representing the planisphere. Such timepieces are called "astrolabes".
BACKGROUND OF THE INVENTION
It has long been known to display astronomical temporal magnitudes such as the phases of the moon, the evolution of the sun and of the planets in the planisphere and in relation to the ring of the Zodiac signs, the eclipses of the sun and of the moon, etc. Horological mechanisms have been designed, e.g. for use in monuments and in astrolabes of smaller size, that can be accommodated on a table.
But the designing of astrolabes of wrist-watch size has always run into considerable difficulties, since the reduced dimensions and the need for sturdiness and reliability in such timepieces is difficult to reconcile with the complexity and the degree of precision that are expected of an astrolabe operating in a satisfactory manner and displaying the astronomical magnitudes with the required accuracy.
SUMMARY OF THE INVENTION
More particularly, as regards accuracy, this could be improved, roughly, by bettering the gear-ratio between the drive mechanism that acts as temporal reference and the astronomical magnitude indicator. This, however, can only be achieved by increasing the number of gear wheels of the reducing train, something that is of course imcompatible with miniaturization to wrist-watch size. Even if a train of differential or planetary gears were used, enabling selection of substantial reduction ratios, it is not possible to achieve both the required degree of miniaturization and accuracy, particularly if it is desired to display several astronomical temporal magnitudes at the same time.
The invention seeks to provide an astronomical watch that can be worn on the wrist and which can combine small size and high accuracy, while endowed with the sturdiness and reliability that can be expected of a wrist-watch.
The invention accordingly provides such an astronomical watch which comprises a temporal reference having a mechanical output which is coupled, via an epicyclic train of gearing, to at least one astronomical magnitude indicator, the ring gear and the driving central wheel of said train of gearing being coupled to said temporal reference, characterized in that said epicyclic train of gearing includes, for each astronomical magnitude indicator, a gear means comprising multiple rotary elements and having a predetermined reduction ratio.
The insertion, between the temporal reference and the astronomical magnitude indicator(s), of gear means borne by the planet wheel carrier of the epicyclic train of gearing leads to a reduction of the volume occupied by the reduction mechanism. This in turn enables a larger number of reducing rotary components to be used and hence greater accuracy of the arrangement. The improvement made by the invention thus results, in the final analysis, in the choice of a compromise between the size of the reduction mechanism (i.e. the number of gears used) and the degree of accuracy achieved which may be considerable despite the fact that the arrangement can be housed in the casing of a wrist-watch. By way of indication, the duration of the tropical year may be displayed with an error margin of less than one second and the duration of the synodic year may be indicated to within 0.05 second as a result of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be better understood on reading the following description with reference to the accompanying drawings in which:
FIG. 1 shows the display arrangement of a watch according to the invention;
FIG. 2 is a partial cross-section of this watch, with certain parts omitted for the sake of clarity;
FIG. 3 shows on an enlarged scale the anti-friction bearing that acts as a suspension for the epicyclic train in its supporting annulus;
FIG. 3A illustrates on a large scale a detail of FIG. 3;
FIG. 4 is a diagrammatic plan view of the various g
REFERENCES:
patent: 246061 (1881-08-01), Blair
patent: 463101 (1891-02-01), Cory
patent: 1153492 (1915-09-01), Hoitinga
patent: 2128970 (1938-09-01), Smyser et al.
patent: 4435795 (1984-03-01), Frank
patent: 4548512 (1985-10-01), Erard
Giger Urs
Oechslin Ludwig
Sporing Jorg
Miska Vit W.
Ulysse Nardin S.A.
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