THE HISTORY OF BLANCPAIN

IN TIME
day at a time. There is an interesting portion
of this gear, I, which serves a vital
programming function. The dates “31” and
“1” both have the same single digit, of
course, the “1”. It is necessary, therefore,
during these days that the “1” digit remain
in place and not advance. Naturally, the
remainder of the mechanism upstream to
the 24 hour wheel will be dutifully rotating
and producing a one tooth advance nonetheless.
How, therefore, can the advance of the
single digit date disc be paused at “1”
during this “31” through “1” period? The
answer is found in the area shown in the
diagram where it appears most of two teeth
are missing. Starting from the last full tooth
before the reduced teeth area and moving
clockwise, what is shown is the tooth for the
date change from “30” to “31”, the stub
tooth for “31”, stub tooth for “1” and finally
the full tooth to change from “1” to “2”.
The position of the stubs serves as a form of
program, insuring that no change in the “1”
digit will take place from “31” to “1”.
The system for changing
the tens disc (Fig. 5).
Here another form of program wheel is
used. This one is shown as K, consisting of
stubs protruding from a disc that turns
clockwise with the intermediate wheel, H.
Logically these stubs are placed at 10 day
intervals except between 30 and 1 where
there is a two day interval, since the tens
digit “3” remains in place for only two
days, “30” and “31”.
WHEN ALL OF THESE SYSTEMS ARE CONSIDERED TOGETHER
The stubs engage the four tooth gear, L,
located below. Attached to the four tooth
gear, L, is the tens disc. Thus, when each
stub engages one of the four teeth, the tens
disc moves one digit to the next of the four
(“0”, “1”, “2”, or “3”) positions.
The system for rapid date correction
via the crown (Fig. 6).
IT CAN BE SEEN THAT THE BLANCPAIN LARGE DATE MECHANISM
TRULY WARRANTS THE LABEL “COMPLICATION”.
Fig. 4
The date change for single digits (cont.).
J
I
K
L
The rapid date change system consists of a
gear train running from gear M, at the
crown end, to an engagement at the left
with the 31 tooth wheel, H. As the crown is
turned, in the date change position of
course, this train turns, advancing the 31
tooth train.
The system must be configured, however,
to advance the dates only when the crown is
Fig. 5
The system for changing the tens disc.