The extension type of Constant Force Spring represents the most basic, yet most versatile, type of constant force spring. It is a pre-stressed flat strip of spring material which is formed into 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. A constant torque is obtained when the outer end of the spring is attached to another spool and caused to wind in either the reverse or same direction as it is originally wound.
The full rated load of the spring is reached after being deflected to a length equal to 1.25 times its diameter. Thereafter, it maintains a relatively constant force regardless of extension length. The load is basically determined by the thickness and width of the material and the diameter of the coil.
Lee Spring offers Stock Constant Force Springs in four Life Cycle ranges: 2500, 4000, 13000 and 25000. Each spring is a roll of high yield Type 301 Stainless Steel strip exerting a nearly constant restraining force to resist uncoiling. We can also provide Custom Constant Force Springs, made to your specification.
