In the first escapement invented and, indeed, in some actually employed
to-day for certain kinds of timekeepers, we notice during the locking a
retrograde movement of the escape wheel; to this kind of movement has
been given the name of _recoil escapement_. It was recognized by the
fraternity that this recoil was prejudicial to the regularity of the
running of the mechanism and, after the invention of the pendulum and
the spiral, inventive makers succeeded in replacing this sort of
escapement with one which we now call the _dead-beat escapement_. In
this latter the wheel, stopped by the axis of the regulator, remains
immovable up to the instant of its disengagement or unlocking.
In the third category have been collected all those forms of escapement
wherein the escape wheel is locked by an intermediate piece, independent
of the regulating organ. This latter performs its vibrations of
oscillation quite without interference, and it is only in contact with
the train during the very brief moment of impulse which is needful to
keep the regulating organ in motion.
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