Japanese house clock with two escapements

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Japanese house clock with two escapements
Manufacturer	(unknown)
Production years	(unknown)
Production location	Japan

This clock indicates the time on the old Japanese system in which the periods of daylight and darkness are each divided into six intervals. On this system day and night hours are of different lengths, and in this clock two separate escapements, each complete with crown-wheel, verge and foliot balance, are provided, one being in use during the daytime and the other at night. The change-over at dawn and dusk is automatically carried out by the striking mechanism.

[edit] How it works

Two crown wheels on one arbor are driven by the going train of wheels, and as the clock is striking the hour corresponding to dawn or dusk a pin in the count-wheel of the striking train engages with a pinion of six leaves and turns through one-sixth of a revolution. On the same axis as this pinion are two triangular cams, and these cams move levers which engage with bottom pivots of the verges, one verge being allowed to fall into its working position while the other one is lifted from engagement with its crown wheel. To allow for the variation in the length of the days and nights the weights on the foliot balances are shifted along the arms at intervals of 15 days. The clock has a single hand mounted on a rotating inner dial which is tapped with a number of holes, into any one of which the pin discharging the alarm can be screwed. The clock strikes the ‘hours’ in the usual Japanese sequences of 9, 8, 7, 6, 5, 4 from midnight to noon and again from noon to midnight, and gives a singe stroke each half ‘hour’.

[edit] Memories

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[edit] In the Science Museum's Records

Inv. No: 1937-889