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The announcement for the patent of a battery driven watch using a tuning fork as timing device in 1953 by ‘Bulova’ on top of the development of a working electro-mechanical movement by ‘LIP’ and ‘Elgin’ in 1952 hit the traditional Swiss watch industry extremely hard. Whereas after the first impact of these news, most Swiss watch manufacturers decided to ignore what seemed to be exotic and short lived systems, other manufacturers such as Omega and especially Ebauches SA (ESA), started almost immediately efforts to pursue their own paths towards an electric watch. It must also be noted, that ESA had a great amount of capital at their disposal to engage in ‘exotic’, horological research, whereas other Swiss watch manufacturers needed to concentrate their efforts to stay competitive (3).
The first battery driven Swiss watches – caliber ‘Pre 475’
Thus, the work on the first Swiss electric prototype movements started in 1952 under the direct supervision of André Beyner and René Besson at ESA and few years later and independently at Battelle for Omega. Swiss developments involving a tuning fork resonator were initially scared off by the very sophisticated ‘Bulova’ patent of 1953, but will resume in the early 1960s at the Centre Electronique Horloger (CEH) and at ESA. It is undeniable, that the electro-mechanical ‘LIP/Elgin’ prototypes were the working base for these early Swiss developments, the electro-mechanical system leaving enough area of research, further development and variability. The overall construction parameters seemed straight forward, as with the ‘LIP/Elgin’ system, the battery and the interlinked electric circuitry would need to ensure isochrone balance wheel oscillations, the battery replacing the main spring as energy source.
The research department of ESA managed to get working and wearable prototypes by 1954. These first proofs of principles, which had not yet attributed caliber designations, had either a rechargeable battery integrated into the case back, later designated with (Version A (Accumulator); P1-V1) or one non-rechargeable battery placed adjacent to the watch case inside a large bracelet link (Version B (Battery); P1-V2).
Caliber 475 A/B
With the refinement of the caliber and the technology transfer from the proofs of principles to industrial production the biggest steps of the development were fulfilled by 1958/59. But the movement is not the only piece of a watch which needs to be developed and adapted. Especially for the introduction of a new system on the market, it was crucial to adapt the design of the watch to the fashion of the day.
It has been tried to integrate the slowly evolving space-age designs into the very first prototype of 1954, which shows an octagonal case shape, not seen in a Swiss wrist watch since the Art Deco period. The designs for the future Swiss electro-mechanic watch were also dependent on the possibility to house the battery.
The layouts (not the finishing) of these prototypes correspond already to a great degree to the marketable versions, but even then, it was not yet clear how to functionally and aesthetically place the batteries.
The differentiation between version ‘A’ (Accumulateur, rechargeable battery) and ‘B’ (Batterie) has been retained and in these prototypes clearly marked on the dial. The designs used in this phase of development are clearly inspired by the design language of Richard Arbib for the electric Hamilton watches marketed in 1958.
Caliber L4750 / L4751
The first successful Swiss attempts to manufacture electromechanical wrist watches were test versions which were not suited for mass production. The intermediary steps included the design of the watch case and the definitive placement of the batteries. Latter had to enable the end consumer to change the battery himself, without the need for consulting a service center. As stated by Ebauches SA in one of their ads of the period, it took almost 10 years to develop a saleable electro-mechanical caliber with a practical and modern case. The first marketed watches featured the finalised electro-mechanical movement L4750. Once the movement showed its final setup in 1960, both battery alimentation versions were marketed. Upon presentation of the L4750 samples at the Basle Fair of 1960, there were already planned modifications for the caliber. Its successor L4751 would feature a hacking second system to synchronise the watch more precisely. The production periods of these watches was extremely short, as by the end of 1961 Lip introduced an improved electromechanical system which was more reliable.
Despite their short production period these movements have been used by over 80 brands or retailers. Also, there are two versions of both movements with 12 or 13 jewels respectively, latter version can also be found with a chronometer certification (1).
Dynotron Caliber
The first battery driven electromechanical calibers such as the LIP R27, and the Ebauches SA L4750/51 had one major flaw. One specific electric contact was oxidising and sometimes sparking when in use, which would wreck the movement and increased the energy draw from the battery. To avoid this problem André Beyner’s team at ESA thought of integrating a germanium transistor (2).
ESA already had a pilot facility to fabricate germanium transistors starting from 1958, using a license from Phillips (NL), who licensed the procedure from Western Electric / Bell Labs (USA) already from 1952 (2).
The work on the new electromechanical caliber which was planned to replace the L4750/51, started in 1960, with a patent already submitted in 1962, by the two ESA engineers André Hug and René Meister. The marketed version of this new caliber was named ESA 9150, which was officially he first caliber with the prefix ‘ESA’ and the system itself was named ‘Dynotron’. The ‘Dynotron’ system was marketed in 1967 and comparably with its predecessor, it was used by over 30 manufacturers. However, to the contrary of the L4750/4751 systems, the Dynotron calibers were used well into the 1970s as cheap, electric alternative to the rising, and much more expensive Swiss quartz watches. One very special variant of the ‘Dynotron’ system is the ESA 9174 caliber, which features jumping hours and minute cylinders in a drum like layout. It was mounted inside driver style cases and distributed by Derby, the in-house brand of Ebauches SA starting 1974 and Jaz, a french brand known for fancy 1970s style watches (2).
Ref.:
- Orologi Elettrici
- Personal comunication with a former Executive Vice-President of Ebauches SA, in charge of Research & Engineering.
Electric Watch Prototypes 