Fusee
From Wikipedia, the free encyclopedia
A fusee is a cone-shaped, grooved pulley used together with a barrel that contains a mainspring.
The first spring-powered clocks are thought to have been invented in about 1510 by Peter Henlein of Nuremberg, Germany). These had the problem of slowing down when the mainspring unwound. The force of the mainspring is greater when fully wound than when it is almost run down. To solve this problem, Jacob Zech of Prague, in about 1525, used a fusee, or spiral pulley, to equalize the uneven pull of the spring.
The verge watch with fusee was used for the first 250 years of watch and clock manufacture.
Due to advances in spring metallurgy around 1760, Jean-Antoine Lepine dispensed with the bulk and complexity of the fusee, using a "going barrel" to power the gear train directly. As a result, during the 18th century, France continued to pursue thinner and smaller watches, and England continued to use and refine their large and robust full-plate movements with fusees.
