CONSTANT FORCE SPRINGS
Constant force springs are a special variety of extension
spring. They consist of a spiral strip material with built-in
curvature so that each turn of strip wraps tightly on its inter
When the strip is extended (deflected) the inherent stress
resists the loading force, just as in a common extension spring,
but at a nearly constant (zero) rate.
The constant force spring is well suited to long extensions with
no load build-up. In use, the spring is usually mounted with the
inside diameter tightly wrapped on a drum and the free end attached
to the loading force, such as in a counterbalance
This relationship can be reversed, however, with the free end
mounted stationary and the spring itself providing the working
force, as with carbon brushes in electrical apparatus.
Considerable flexibility is possible with constant force springs
because the load can be multiplied by using two or more strips in
tandem, back-to-back, or laminated.
Type 301 stainless steel.
Be sure to allow at least 1 1/2 coils of material on the drum at
full extension. The spring ID will wrap tightly on the drum so that
in most applications no fastening method on the drum is