Mechanical engineering with differential gears. The medieval Chinese horologist and engineer Su Song (1020–1101 AD) incorporated an escapement mechanism into his astronomical clock tower two centuries before escapement devices were found in medieval European clocks. He also invented the world's first known endless power-transmitting chain drive. During the Islamic Golden Age (7th to 15th century), Muslim inventors made remarkable contributions in the field of mechanical technology. Al-Jazari, who was one of them, wrote his famous "Book of Knowledge of Ingenious Mechanical Devices" in 1206 and presented many mechanical designs. Al-Jazari is also the first known person to create devices such as the
Escapement of this escapement over the lever are of an uncertain value. In an effort to attract publicity, in recent decades some high end mechanical watch makers have introduced new escapements. None of these have been adopted by any watchmakers beyond their original creator. Based on patents initially submitted by Rolex on behalf of inventor Nicolas Déhon, the constant escapement was developed by Girard-Perregaux as working prototypes in 2008 (Nicolas Déhon was then head of Girard-Perregaux R&D department) and in watches by 2013. The key component of this escapement is a silicon buckled-blade which stores elastic energy. This blade is flexed