Horology: time measuring systems or devices – Astronomical – With navigational display
Reexamination Certificate
1997-12-10
2001-06-19
Roskoski, Bernard (Department: 2859)
Horology: time measuring systems or devices
Astronomical
With navigational display
C368S028000
Reexamination Certificate
active
06249485
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates to mechanical clocks. More particularly, the invention relates to a mechanical device for converting one time base to another.
2. Description of the Prior Art
A clock which displays multiple intervals, such as hours and days, requires a mechanism for converting the basic time base, such as the wing of a pendulum, into the displayed intervals, e.g. hours. This is normally accomplished with a gear train, which works well when the intervals displayed are integer multiples of the period of the time base. However, such integral multiple relationship is not achievable when the displayed intervals do not bear a simple rational relationship to one another. This is the case, for example, when the intervals displayed are constants, such as lunar months and solar years, which are approximately 29.5303882 days and 365.242198 days, respectively. The calendar is arranged to add a day each fourth year to compensate roughly for this mismatch between the calendar year and the solar year, i.e. an extra day is added to the month of February during leap years. Such factors are also readily taken into account with electronic time keeping systems. However, in a mechanical clock that uses a gear train, these constants must be approximated by a ratio of numbers. If conventional mechanical techniques are used, a gear train having a very large number of gear teeth is required to achieve an accurate approximation of such constants.
It would be advantageous to provide a mechanical device that achieves an accurate approximation of such constants as lunar months and solar years without requiring a complex gear train, e.g. a gear train having a very large number of gear teeth.
SUMMARY OF THE INVENTION
The invention provides a mechanical device for converting one time base to another without using gears to do so. The preferred embodiment of the invention is a mechanical adder that adds a constant into an accumulator at regular intervals. The interval is generated by the overflow of the accumulator. For example, consider the case where a signal is to be generated once every solar year from a wheel that rotates once per day. In such case, the fractional number {fraction (1/365.242198)} is added to the accumulator each day by the rotation of the day wheel. Whenever the accumulation overflows, the one-year signal is generated. The fractional portion of the accumulated sum remains in the accumulator, such that round-off errors do not accumulate over time. The preferred adder is digital, such that this computation may be carried out to any desired level of precision. Additionally, the same design, but with a different constant, may be used to generate other intervals (e.g. for lunar months).
REFERENCES:
patent: 165432 (1875-07-01), Terry
patent: 3031654 (1962-04-01), Galen
patent: 3316706 (1967-05-01), Kilburg
patent: 3524313 (1970-08-01), Wood
patent: 3807166 (1974-04-01), Meitinger
Glenn Michael A.
Roskoski Bernard
The Long Now Foundation
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