WatchTime - August 2012

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Patek Philippe Reference 5204
A COMPARISON OF THE
TWO ISOLATORS:
Conventional isolator in caliber
CH 27-70/150 (“octopus”)
A conventional split-seconds isolator needs two
oppositely acting springs. One of them is affixed
below the split-seconds wheel; the other is
attached above it. These two springs alternately
control the connection between the split-seconds
wheel and the chronograph’s center wheel. This
elaborate construction burdens the split-seconds
wheel with additional moved mass, which in turn
affects the balance’s amplitude. Furthermore, the
bearing for the chronograph’s axle is also additionally
stressed and the height of the movement
must be increased.
Isolator in the new caliber
CHR 29-535 PS Q
In Patek Philippe’s new construction, only one
spring, above the split-seconds column wheel and
working in two directions, is needed. The new
split-seconds mechanism is simpler to construct.
Its principal advantage is that the weight of the
springs is shifted from the split-seconds, which
must be moved, to the static column wheel and
the plate. This construction takes much of the
load off the bearing for the chronograph’s axle
and makes the movement thinner than it would
be with a conventional isolator.
58 WatchTime August 2012
The so-called “octopus” isolator
in caliber CHR 27-70/150
satisfy Patek Philippe’s needs until the 1980s. When the ébauches
ran out, Patek Philippe chose as its new supplier the
renowned Nouvelle Lémania ébauche manufacturer. The agreement
between Patek and Lémania regulated delivery of all basic
components for caliber 2320, including the plate. Everything
else was handled by Patek Philippe on its own premises in Geneva.
Patek Philippe modified more than 60 percent of the components
delivered by Lemania. Reference 3970, which had a
chronograph and perpetual calendar, debuted at the Basel fair in
1986. Connoisseurs had to wait 10 years for the split-seconds
version, Reference 5004.
That watch was powered by Caliber CHR 27-70/150, 8.86
mm tall and containing 404 components. The split-seconds
mechanism, which was developed by the manufacture, included
an unconventional component with a shape that strongly resembled
the tentacles of an octopus. This so-called “octopus
wheel” performed an important and innovative function. In ordinary
mechanisms, the little ruby roller of the split-seconds
lever continues to run around the split-seconds heart when the
split-seconds hand is stopped. This saps energy and therefore reduces
the balance’s amplitude. Patek Philippe counteracted this
not inconsiderable loss of energy by equipping caliber CHR 27-
70/150 with an isolator. This component completely uncouples
the split-seconds wheel from the chronograph’s center wheel
A Patek Philippe split-seconds chrono from the
1920s with movement by Victorin Piguet