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Used in antique spring-powered mechanical watches and clocks, a fusee is a cone-shaped pulley with a helical groove around it, wound with a cord or chain which is attached to the mainspring barrel. Fusees were used from the 15th century to the early 20th century to improve timekeeping by equalizing the uneven pull of the mainspring as it ran down. Gawaine Baillie stated of the fusee, "Perhaps no problem in mechanics has ever been solved so simply and so perfectly."〔 ==History== The origin of the fusee is not known. Many sources erroneously credit clockmaker Jacob Zech of Prague with inventing it around 1525,〔, p.250〕 but it actually appeared with the first spring driven clocks in the 15th century.〔, p.127-128〕〔, p.121〕 The idea probably did not originate with clockmakers, since the earliest known example is in a crossbow windlass shown in a 1405 military manuscript.〔 Drawings from the 15th century by Filippo Brunelleschi〔, author is Curator of Horology at the British Museum〕 and Leonardo da Vinci〔, p.227〕 (left) show fusees. The earliest existing clock with a fusee, also the earliest spring-powered clock, is the ''Burgunderuhr'' (Burgundy clock), a chamber clock whose iconography suggests that it was made for Phillipe the Good, Duke of Burgundy about 1430, now in the Germanisches Nationalmuseum〔〔 The earliest definitely dated fusee clock was made by Zech in 1525. The word fusee comes from the French ''fusée'' and late Latin ''fusata'', 'spindle full of thread'. Springs were first employed to power clocks in the 15th century, to make them smaller and portable.〔〔 These early spring-driven clocks were much less accurate than weight-driven clocks. Unlike a weight on a cord, which exerts a constant force to turn the clock's wheels, the force a spring exerts diminishes as the spring unwinds. The primitive verge and foliot timekeeping mechanism, used in all early clocks, was sensitive to changes in drive force. So spring-driven clocks slowed down over time as the mainspring unwound. This problem is called lack of isochronism. Two solutions to this problem appeared with the first spring driven clocks; the ''stackfreed'' and the fusee.〔 The stackfreed, a crude cam compensator, added a lot of friction and was abandoned after less than a century.〔Milham 1945, p.230〕 The fusee was a much more lasting idea. As the movement ran, the tapering shape of the fusee pulley continuously changed the mechanical advantage of the pull from the mainspring, compensating for the diminishing spring force. Clockmakers apparently empirically discovered the correct shape for the fusee, which is not a simple cone but a hyperboloid.〔, p.29〕 The first fusees were long and slender, but later ones have a more squat compact shape. Fusees became the standard method of getting constant force from a mainspring, used in most spring-wound clocks, and watches when they appeared in the 17th century. At first the fusee cord was made of gut, or sometimes wire. Around 1650 chains began to be used, which lasted longer.〔 Gruet of Geneva is widely credited with introducing them in 1664,〔 although the first reference to a fusee chain is around 1540.〔 Fusees designed for use with cords can be distinguished by their grooves, which have a circular cross section, where ones designed for chains have rectangular-shaped grooves. Around 1726 John Harrison added the maintaining power spring to the fusee to keep marine chronometers running during winding, and this was generally adopted. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Fusee (horology)」の詳細全文を読む スポンサード リンク
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