60
61
The Cylinder escapement represented a small revolution in the
history of portable timekeeping since this escapement functioned
with far more precision than the Verge escapement
*
that had
been in use until then. The balance
*
in a Cylinder escapement
can oscillate much further (amplitude
*
) and bothersome
losses due to friction
*
are much smaller than those of the
recoiling
*
Verge escapement. The Cylinder escapement
is a so-called Frictional-rest escapement
*
since the escape
wheel stands still—resting—during the complementary
arc of the balance.
The base idea goes back to 1695 to famed English
watchmaker Thomas Tompion
*
. Around 1750, Tompion’s
pupil, friend, and later partner George Graham
*
achieved
further improvement on this escapement for pendulum clocks
using enhanced manufacturing techniques, giving direction to the
whole of watchmaking at the time. Graham is one of watchmaking’s
most famous watchmakers thanks to the Graham escapement
named for him, an ingeniously simple Frictional-rest escapement for
pendulum clocks.
side for a moment by the balance’s Discharging pallet
*
and the
escape wheel can pass its impulse to the locking pallet. After that,
the escape wheel is stopped precisely at the next tooth by the locking
pallet
*
via the recoiling detent arm. When the balance oscillates
back, the crooked, fine gold spring of the detent arm allows the
unlocking pallet to pass. There are numerous variations of the
Chronometer escapement from England, for example with detent
bar and lever arm.
The Chronometer escapement was an important step toward the
precision timepiece. However, this type of escapement is not the only
decisive element for the rate precision of a watch or clock. This is also
dependent upon the temperature compensation of the balance and
the quality of the balance spring
*
.
The fact that the Chronometer escapement could not assert itself is
chiefly due to two things: for one, it was much more elaborate
than the Club-tooth Lever escapement developed a little later and for
another it was much more receptive to shocks. Also, the balance did
not restart by itself if it was stopped by a blow. And if the balance
was made to go faster by an outside blow, it very easily began
»galloping«—which means that too-large oscillations of the balance
saw it passing several teeth (rather than just the one it should). In
summary, it must be underscored that to this day the Chronometer
escapement remains the most precise—if the most complicated—
escapement for portable timekeepers.
English Lever escapement
(from 1792)
Cylinder escapement
(from 1695; improvement from 1720)
With the development of the first frictional-rest
*
escapements
by Tompion and Graham, rate
*
results improved immensely.
Thus, it was logical for watchmakers to consider how the
balance
*
can be allowed to oscillate even more freely
in precision timepieces.
The Chronometer escapement was probably
developed by Frenchman Pierre Le Roy
*
for a marine
chronometer
*
. As a Simplex-escapement
*
like the
Cylinder escapement
*
, it was supposed to allow the
balance
*
to oscillate as freely as possible. This was achieved
by adding the Discharging pallet
*
and detent arm, which were
placed between the escape wheel and the balance
*
. When the
balance oscillates counterclockwise, the detent arm is pushed to the
The English Lever escapement is
an early form of the jeweled
Lever escapement
*
. It follows
the design elements of the
Graham escapement
*
and was
the basis for the Club-tooth
Lever escapement. The pointed,
thin, oothed wheels were howe-
ver very sensitive, which made
keeping oil on the pallets
*
hard,
and did not encourage an
optimal transmission
*
of energy.
Chronometer escapement
(1766 with spring, 1772 with pivoted detent)
The Development
of the Escapement
Cylinder
Balance
Pallet lever
Escape wheel
Cylinder
escape wheel
Gold spring
Detent arm
Discharging
pallet
Impulse
pallet
Locking
pallet
