The Escapement
The escapement, escape wheel and pallet lever, together with the balance system is the real heart of the movement. The escape wheel and the pallet lever together perform two different but equally important tasks: to control the rate by which the main spring unwinds (oscillator with a stable frequency) and to repeatedly give the balance wheel its needed impulse.
The picture shows the Escape Wheel (705) which is the last wheel in the wheel train that is powered by the Mainspring.
The two tasks are implemented by the geometry of the pallet jewels and Escape Wheel teeth. If not locked by the Pallet Lever, the Escape Wheel would accelerate to a very high speed and the Mainspring would unwind in just a few seconds.
The Escape Wheel (705) pinion is driven by the Fourth Wheel (224). The Escape Wheel in turn interacts with the Pallet Lever (710).
The Wheel Train starts to the left with the Barrel (182) which drives the Center Wheel (201) pinion. The rotation speed is further increased via the Third Wheel (210) to the Fourth Wheel (224), which makes one revolution per minute and has the second hand attached to its arbor. Finally the Fourth Wheel engages the Escape Wheel (230) pinion.
