Escapement and watches. These are described individually below. Although the invention of the crystal oscillator and the quartz clock in the 1920s shifted technological research in timekeeping to electronic methods, major advances in the design of mechanical escapement are still happening. Coaxial escapement, invented by English watchmaker George Daniels around 1974 and patented in 1980 has rather dramatically increased the accuracy and durability of mechanical watches. Yoshikazu Akahane with teams of engineers at Seiko Epson developed the spring drive movement around 1977, and obtained not less than 230 patents between 1982 and the present. The reliability of an escapement depends on
Anchor escapement it unwinds. An escapement in which changes in drive force do not affect the rate is called isochronous. The superior performance of the deadbeat over the recoil is due to improved isochronism. This is due to the different ways changes in drive force affect the swing of the pendulum in the two escapements: When the deadbeat was invented, clockmakers initially believed it had inferior isochronism to the anchor, because of the greater effect of changes in force on the pendulum's amplitude. Recent analyses point out that the nonisochronism of the anchor can cancel the circular error of the pendulum. That