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The new CH28-520 IRM QA 24H chronograph caliber is a self-winding
mechanical movement with a flyback column-wheel chronograph, power
reserve indicator, Annual Calendar, and day/night display.
The chronograph mechanism is based on the venerable column-wheel
principle for controlling the start/stop commands. However, it differs
from classic Patek Philippe column-wheel chronographs by virtue
of a remarkable innovation: The clamps do not control the engagement
of a lever-mounted clutch wheel with the chronograph train but instead
act on a disk clutch that transmit (chronograph running) or interrupts(chronograph
stopped) the power between the fourth wheel and the chronograph
hand. This is a highly reliable solution that eliminates the occurrence
of backlash-induced hand jitter or bouncing because it does not
involve the sudden meshing of teeth when the chronograph is started.
It also replaces the conventional three-wheel chronograph train
that for reasons of wear made it inadvisable to keep the chronograph
running permanently. In this movement, the chronograph-hand can
be used without hesitation as a continuously running seconds hand;
because this has no negative impact on the rate accuracy of the
watch, the subsidiary seconds dial customarily found in many chronographs
is no longer needed.
The chronograph is operated with two buttons. The one at 12:00
starts and stops a measurement. The button at 4:00 is used to reset
the stopped chrono-hand or activate the flyback function when the
chrono-hand is running.
The patented Patek Philippe Annual Calendar is a full calendar
that automatically recognizes months with 30 and 31days, only needs
to be manually corrected once a year. It displays the day of the
week, the date, and the month in three apertures on dial.
This model features an unusual combined minute and hour totalizer
for chronograph. On the 60-minutes totalizer, the red hand counts
the minutes on the two outer concentric scales that are graduated
from 0 to 30 in red, and from 30 to 60 in blue. The blue hand and
the inner scale indicate the duration in hours upto 12 hours.
The model is with platinum case. It features a small diamond between
the lugs at 6:00, the discreet identifier of all of the manufacturer's
platinum cases.
Case diameter: 40.50mm (43.25 mm incl. crown)
Case thickness: 13.55 mm
Yen 6,195,000
Contacts: Patek Philippe Japan Information Center Tel: 03-3255-8109
http://www.patek.com
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