Editing Flip clock (section)

==History==
The flip clock was invented in Germany by {{Ill|Josef Pallweber|de}} in 1890.<ref name="patent"/><ref>{{cite web |last= |first= |date=December 1, 1890 |pages=178-179 |title=Fachblatt für Uhrmacher XIV Jahrgang |url=https://digital.slub-dresden.de/werkansicht/dlf/53992/181 |location=Berlin |publisher=Deutsche Uhrmacher Zeitung |url-status=dead |archive-url=https://web.archive.org/web/20220810233859/https://digital.slub-dresden.de/werkansicht/dlf/53992/181 |archive-date=2022-08-10 |access-date=2025-03-12}}</ref> Unlike the typical [[Analog clock|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]].<ref name="patent">{{cite web |last=Pallweber |first=Josef |date=27 October 1890 |title=Pallweber Patent |url=https://www.flipclockfans.com/docs/Pallweber_Patient_54093_1890.pdf |website=Flip Clock Fans |publisher=Imperial Patent Office |url-status=live |archive-url=https://web.archive.org/web/20250312111923/https://www.flipclockfans.com/docs/Pallweber_Patient_54093_1890.pdf |archive-date=2025-03-12 |access-date=2025-03-12}}</ref><ref>{{cite web |title=Adix Adding Machine Explained – Everything You Need To Know |url=https://history-computer.com/adix-adding-machine/ |website=History Computer |url-status=dead |archive-url=https://web.archive.org/web/20231128085044/https://history-computer.com/adix-adding-machine/ |archive-date=2023-11-28 |access-date=2025-03-12}}</ref>

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|merchant]] and inventor of [[Typewriter|typewriter]] mechanisms, Fitch entered the field of [[Chronometry|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.<ref name="plato">{{cite web |last=Terwilliger |first=Charles O. |date=1964 |title=Eugene L. Fitch and The Plato Clock |url=https://www.flipclockfans.com/docs/Eugene_L_Fitch_And_The_Plato_Clock.pdf |website=Flip Clock Fans |publisher=National Association of Watch and Clock Collectors |access-date=2025-03-12}}</ref>

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|drive shaft]] and adding a [[Ball bearing|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|celluloid]] plates with die-cut "ears" as pivots, thereby eliminating the need for ball bearings, and introducing [[Cam (mechanism)|cams]] to prevent premature hour flips. This final design became the prototype for production models.<ref name="plato"/>

Production of the Plato clock began between 1904 and 1906, financed by Conrad Hubert, president of the [[Eveready Battery Company|American Everready Company]]. The clock was a commercial success, with approximately 40,000 units sold.  The name "Plato" derived from "plate-o," referencing the plate mechanism, though the name was often associated with the philosopher [[Plato]]. Early models were manufactured by the [[Ansonia Clock Company]], with variations including glass domes and alternative [[Wheel train|winding mechanisms]]. A license was granted to a French firm which produced 30-hour and 8-day models of the Plato clock, while German copies by firms like Lenzkircher Uhren Fabrik and Gebr. Junghans soon followed.<ref name="plato"/>

Development of the flip clock continued beyond Fitch's work. Early designs relied on mechanical movements, and material limitations posed durability issues, with the plates often becoming warped beyond repair. By the mid-20th century, electromechanical flip clocks were developed. A significant improvement to the design came from [[Josef Mergenhagen]] in Germany during the 1950s. Initially using a 30-hour [[Jewel bearing|non-jewel]] movement, Mergenhagen upgraded it to an 8-day, 7-jewel mechanism and modernized the case design. After early plastic plates faced similar warping issues to previous clocks, he sourced a superior plastic from a German manufacturer, which resolved the issue of warping and allowed the plates to remain flat under various conditions. His models, marked "J. Mergenhagen West Germany," included both vertical and horizontal versions.<ref name="plato"/>