Constant force, constant torque, constant load springs

It is a pre-stressed flat strip of spring material which is formed into a virtually constant radius coils around itself or on a drum. When the strip is extended (deflected) the inherent stress resists the loading force, the same as a common extension spring, but at a nearly constant (zero) rate. 

As with all spring applications the mounting of the spring is crucial to its effective operation. A constant force spring is usually mounted by first tightly wrapping it on a drum, then attaching the free end to the loading force such as in a counterbalance application. This relationship can be reversed, however, with the free end mounted stationary and the spring itself providing the working force.

The asymmetric design of a constant force spring gives rise to additional interesting possibilities such as tandem or laminar mounting which enables simple doubling of force – or the intriguing back-to-back style of installation which not only multiples force but also balances the asymmetric forces improving stability of the assembly.

Further information on Lee Spring products can be found on their website - www.leespring.co.uk or by following them on Twitter - https://twitter.com/leespringuk