"lever escapement"
by cm

Lever Escapement
Creative Commons Attribution Share AlikeLever Escapement - Credit: Shannon, Wikimedia Commons
Invented by Thomas Mudge in c.1757, the lever escapement leaves the balance wheel free to oscillate, coupling it to the escape wheel only while the impulse is being delivered.  The lever has two pallets which engage the escape wheel at one end, and a fork which catches and releases a pin on the balance wheel at the other end.