In the early 1400s came the invention of the coiled spring or fusee which maintained constantforce to the gear wheels of the timekeeper despite the changing tension of its mainspring.
Constantforce spring hanger is a device which puts invariable tension on the thing it hangs in limited displacement.
恒力弹簧支吊架是一种在限定位移内对被支吊物施以恒定张力的装置。
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Check the wear of the electric brush and see whether the constantforce spring has distorted or not. Over-worn electric brush and distorted force spring should be replaced.