Flip clock

The study, collection and repair of flip clocks is termed horopalettology (from horology – the study and measurement of time and palette – and the Italian "orologio a palette" – Italian for "flip clock").

An electric motor (often synchronous, if directly connected to the AC line) turns two sets of wheels continuously via a reduction gear train: the faster at a rate of 1 revolution per hour, the slower at a rate of 1 revolution per 24 hours.

The faster wheel has connected to it a ring of 60 flat plastic leaves.

A different design features 60 leaves with the numbers 1 to 12 repeated in fives, each leaf falling after 12 minutes.

Many vintage digital clocks with split flap displays cannot be wound back, as the flip mechanism operates only in one direction.

1970s Copal flip alarm clock
Schematic of a split-flap display in a digital clock display
Mechanism of a split-flap alarm clock, removed from its case. The inset shows the metal tab holding back the top flap. The narrow numbered wheel and knobs on the left are the alarm mechanism. This is a synchronous electric clock which is kept to the correct time by the 50/60 Hz AC power grid.
The small hook which retains the hour leaves until the top of the hour can be dimly seen, retracted, in the inset.