Horology: time measuring systems or devices – Chronological – With significant casing or mounting support structure
Patent
1988-04-06
1990-01-09
Miska, Vit W.
Horology: time measuring systems or devices
Chronological
With significant casing or mounting support structure
368220, 368318, 368323, G04B 3700, G04B 1902
Patent
active
048932922
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to electronic watch movements comprising analog time display means and more particularly those having only an hours hand and a minutes hand.
Such movements are generally intended to watches of small size, e.g. ladies' watches. In such watches, it is desirable for the cell to be as close as possible to the center of the watch. To this end, the movement described in swiss patent specification 615068 comprises a bottom-plate on which is provided a central peg on the dial side. On this peg are pivotally mounted the cannon-pinion and the hours wheel, which respectively mesh with the minutes wheel and the minutes pinion. The kinematic connection with the rotor is thus solely provided by the minutes gear. This arrangement enables the center of the movement to be cleared and hence a cell of large diameter to be used, but gives rise to a major drawback: since the cannon-pinion is at the end of the kinematic chain provided by the gear-train and thus, necessarily, has only few teeth, the backlash is quite substantial. As a result, the position of the minutes hand becomes somewhat inaccurate, unless a brake is applied on the cannon-pinion. But such a brake would increase the energy consumption of the watch and a larger cell would then be needed to achieve a corresponding autonomy.
In the specification of Japanese patent application 57-161578, a movement is described having a bottom-plate, a gear-train bridge, a rotor, an intermediate gear and an hours wheel. The center gear has a shaft that is pivotally mounted between the bridge and the bottom-plate and on which a wheel web is frictionally mounted. The shaft takes up the entire height of the movement while the wheel web is housed in a space between the bottom-plate and the cell. This arrangement lends itself to the design of a watch in which the cell extends close to the center without giving rise to a backlash problem with the center gear. But this result is achieved at the expense of the thickness of the cell.
SUMMARY OF THE INVENTION
An object of the invention is to remedy these defects with a constructional arrangement that still makes it feasible for a cell to extend as close as possible to the center of the movement, and with a cell thickness almost equal to the height of the movement.
According to the invention, the invention provides an electronic watch movement comprising a bottom-plate having a central opening, a cell, time display means having indicator hands, a motor and a gear-train connecting the motor to the indicator hands, said gear-train including an intermediate gear, a center gear having a shaft and having a wheel and a pinion solid with said shaft, a minutes gear and an hours wheel, having a pipe, rotatably mounted on said shaft directly over the wheel of said center gear, the wheel of said center gear meshing with teeth on said intermediate gear and extending over said cell, and the central opening in said bottom-plate having a diameter larger than that of the pinion of said center gear.
SHORT DESCRIPTION OF THE DRAWINGS
In the accompanying diagrammatic drawings, in which the same reference numbers are used to designate corresponding parts:
FIGS. 1 and 3 are cross-sections through a part of two movements according to the invention; and
FIGS. 2 and 4 are again cross-sections through a part of the same movements but along a different line.
DETAILED DESCRIPTION
The movement shown in FIGS. 1 and 2 comprises a frame made up of a bottom-plate 1 and of a gear-train bridge 2. Between these two frame elements is mounted a motor, not shown, whose rotor has a pinion that meshes with a first intermediate gear 3, in particular with the wheel 4 thereof. The pinion 5 of gear 3 meshes with the wheel 6 of a second intermediate gear 7 whose pinion 8 consists of a toothed dish-like disc solid with shaft 9 of gear 7. Shaft 9 has two pivots 10 each engaged in a jewel 11. One of these jewels is set into a hole provided in bottom-plate 1 at the center of a boss 12 that projects inwardly of the movement. Bott
REFERENCES:
patent: 4087957 (1978-05-01), Miyasaka et al.
patent: 4249251 (1981-02-01), Wutarich
patent: 4335454 (1982-06-01), Yamada
patent: 4496246 (1985-01-01), Ota et al.
Patent Abstracts of Japan, vol. 6, No. 265 (P-165) (1143), 24 Dec. 1982.
Eta SA Fabriques d'Ebauches
Miska Vit W.
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