thumb|Solari Cifra 3 designed by [[Nani Valle|Nani and Gino Valle with graphic design input form Massimo Vignelli (1965)]]
A flip clock (also known as a "flap clock") is an electromechanical, digital timekeeping device which displays the time through a split-flap display, where numbers are revealed by flipping or rotating a series of plates or leaves.
History
The flip clock was invented in Germany by in 1890. Unlike the typical analog clocks at the time, Pallweber's design used double-sided metal tablets suspended in drums: a minute drum with 60 tablets and an hour drum with 24 tablets. Each tablet displayed the upper half of a number on one side and the lower half of the next number on the reverse, so that when one tablet stood upright and the next hung down, they formed a complete number visible through a reading window. Production of Pallweber's flip clock design began around 1894 at Lenzkirch Clock Factory.
The flip clock saw further development by American inventor Eugene L. Fitch, who patented the Plato clock in 1902. After a varied career including work as a merchant and inventor of typewriter mechanisms, Fitch entered the field of horology with no prior experience. His Plato clock was designed to provide an instant time display using two sets of rotating plates: one for hours and one for minutes, intended not only for timekeeping but also as a method of advertising. Fitch's original design featured vertical disks holding the plates, with each plate marked "ADV" on its back, reflecting his initial vision for clocks as an advertising medium. Subsequent designs were no longer marked in this way.
Fitch continued to develop the Plato clock over the course of four patents. The first in 1902 introduced the basic concept, but the vertical disk arrangement posed aesthetic and functional challenges. His second patent in 1903 shifted the disks to a horizontal position, improving the layout of the clock and allowing for larger numbers by making use of both sides of the plates. This change would introduce new mechanical issues, however, such as the plates failing to stack properly. Fitch addressed this problem in his third patent, also in 1903, by tilting the drive shaft and adding a ball bearing to reduce friction. At this point in development, the increased complexity of the clock had made production unviable, with three sets of plates containing over 900 parts. Fitch's fourth patent in 1904 refined the design using lightweight celluloid plates with die-cut "ears" as pivots, thereby eliminating the need for ball bearings, and introducing cams to prevent premature hour flips. This final design became the prototype for production models.
File:Cifra 5 digital flip clock designed by Gino Valle (1957).jpg|Solari Cifra 5 clock by Nani and Gino Valle (1957)
File:Paolo Monti - Servizio fotografico - BEIC 6355499.jpg|Cifra 5 internal mechanism
File:Clock-Lowicz-150604.jpg|Cifra 23 by Solari di Udine, known for its stylish design, digital flip clock dated Sixties, used in airport Paris-Orly and Warszawa Centralna railway station.
File:Sony Digimatic 8FC-59W radio alarm clock 20060526.png|A 1969 radio alarm clock (Sony Digimatic 8FC-59W) with an early digital display
File:Copal japan 1970s Alarm flip number electric clock.jpg|1970s Copal flip alarm clock
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See also
- Cifra 3
- Twemco
- Digital sundial