Timeline  /  The two-disc big date is patented
1991

The two-disc big date is patented

Invention

On 22 August 1991 Jaeger-LeCoultre filed the patent for a date shown by two discs, a units ring with a tens cross inside it, each in its own window; the inventors were Roger Guignard and Günter Blümlein, and the first watch to use it was the Lange 1.

231blank5678901234Tens disca cross carrying 1, 2, 3and a blank for thefirst nine daysUnits ring0 to 9 on a ring;the cross tucksunder its edgeWindowone numeral fromeach disc showsthrough itTwo planesthe cross lies justunder the ring; wherethey overlap, the ringis on topDial lifted off: each digit has a disc of its own
The patent drawing, redrawn: a ring carrying 0 to 9 and, tucked under its edge on a lower plane, a cross carrying 1, 2, 3 and a blank. One numeral from each shows through the two windows.
The need
A date disc with 31 numerals gives each numeral a thirty-first of the circle, so the digits in a date window are tiny. To make them big the date had to be split into two digits, each on a disc of its own.
Made by
Manufacture Jaeger-LeCoultre, Le Sentier, within Günter Blümlein’s LMH group; inventors Roger Guignard and Günter Blümlein. German priority 22 August 1991 (DE 41 27 825 C1); European patent EP 0 529 191, granted 18 September 1996.
What was new
A ring-shaped units disc with 0 to 9 and a small tens disc with 1, 2, 3 and a blank, lying inside the ring’s outline on a lower plane, each driven by its own programme wheel from one date wheel. The windows are cut between the tens numerals, which gives the tens disc its cross shape. From the 31st to the 1st the units ring stays put and only the tens disc moves.
Worth knowing
The patent was held by Jaeger-LeCoultre, not by Lange, and under Blümlein only Lange used it; the other Richemont houses adopted the big date after his death in 2001. Glashütte Original answered in 1997 with two concentric discs on one plane and no bar between the digits.
Where it is now
The patent texts are on Google Patents and Espacenet; the mechanism is in every Lange 1.

Historian’s noteThe patent cites no earlier two-digit date as prior art, and the first watch to carry it was shown in October 1994. The big date page explains the mechanism with diagrams.

SourcesEuropean patent EP 0 529 191 · German patent DE 41 27 825 · Deployant, big date watches

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