The clock spring is also known as power spring. This spring is identified by coils of strip materials, which are stored in band, case, barrel, and connected to a shaft, or a central arbor. The materials starts winding flat against the shaft, when it is rotated. This action produces an increasing torque for turns as it can be wounded until the material finishes off.
There are two types of power or clock springs – conventional and pre-stressed power springs.
Conventional power springs produce high torque per deflection, and have normal residual stresses. Pre-stressed power springs produce low force gradient than the conventional power springs. These springs can provide twice turns than the conventional power springs. Pre-stressed power springs have compact, and lightweight designs.