Horology: time measuring systems or devices – Displays or display device details – Dial or hand
Patent
1995-02-16
1997-11-11
Roskoski, Bernard
Horology: time measuring systems or devices
Displays or display device details
Dial or hand
G04B 1916
Patent
active
056871406
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a timepiece capable of switching the time display thereof on a before-noon/after-noon basis, and a display switching mechanism thereof.
BACKGROUND OF THE RELATED ART
Among conventional timepieces, a 12-number timepiece is predominant which has an hour hand making two turns a day. Such a timepiece has a dial plate equally divided into twelve and allows the time to be read on the basis of an hours symbol pointed by the hour hand. The problem with this kind of timepiece is that a person cannot distinguish the before-noon and the after-noon at a glance since hours and minutes are displayed by exactly the same symbols both the before-noon hours and the after-noon hours.
In light of the above, some timepieces are provided with an hour hand making a single turn a day in order to display the time on a 24-hour basis. However, since the display area available with a wrist watch, watch or similar portable watch is small, dividing it into twenty-four would render the time difficult to see. Moreover, a person accustomed to a predominant 12-numeral timepiece is apt to mistake the time.
It is, therefore, preferable to preserve the conventional hour hand turning round on a 12-numeral basis and, in addition, to distinguish the before-noon hours and the after-noon hours in a sure and easy way.
A mechanism for switching the time display to distinguish the before-noon and the after-noon, particularly a display switching mechanism for a wrist watch, is taught in Japanese Utility Model Laid-Open Publication No. 63-187088 by way of example. The mechanism disclosed in this Laid-Open Publication has an operating wheel making one rotation a day. An actuator pin is studded on the operating wheel and received in a switching window formed through a display plate. When the actuator pin completes one rotation within the window, the display plate moves a predetermined angle in a reciprocating motion. As a result, the display is switched from the before-noon to the after-noon and vice versa.
In the above mechanism, a jump and hold spring moves along a tooth portion formed in the inner periphery of the display plate and then gets it over, at each transition from the before-noon to the after-noon, and vice versa. This, however, brings about a problem that at the time of display switchover, numerals "1" to "12" representing the before-noon hours and numerals "13" to "24" representing the after-noon hours overlap each other little by little, making it difficult to see the time.
Although the switchover from the after-noon display to the before-noon display may proceed slowly since it generally occurs while a person is asleep, the switchover from the before-noon display to the after-noon display should preferably be sharp.
It is, therefore, an object of the present invention to provide a timepiece having an hour hand moving on a 12-numeral basis like a conventional hour hand, and allowing the before-noon display and the after-noon display to be distinguished surely and easily. Another object of the present invention is to provide a convenient timepiece capable of switching the time display thereof from the before-noon to the after-noon instantaneously, and a display switching mechanism thereof.
DISCLOSURE OF THE INVENTION
In accordance with the present invention, a rotation is transferred from an hour wheel to a sectorial cam via an operating wheel, thereby causing the cam to make one rotation a day. A lever is held in contact with the cam and constantly is biased by a spring. The lever moves in a reciprocating angular motion due to the sectorial shape of the cam. The reciprocation of the lever matches a difference between a larger diameter portion and a smaller diameter portion forming the cam. A movable dial plate is engaged with the lever and, therefore, is also moved in a reciprocating motion. The angular movement and position of the movable dial plate are determined by the reciprocation of the lever.
In the event of a change from the before-noon display to the after-noon displa
REFERENCES:
patent: 355461 (1887-01-01), Morton
patent: 374605 (1887-12-01), Lewis
patent: 395696 (1889-01-01), Ethridge
patent: 403338 (1889-05-01), Fischer
patent: 1424195 (1922-08-01), Demko et al.
patent: 3404527 (1968-10-01), Tripet et al.
Asao Tetsushi
Sekine Kiyose
Orient Watch Company Limited
Roskoski Bernard
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