Torsion springs

Torsion springs are a type of coiled spring that work via a rotational motion known as torsion. They are used when there is a need for rotational movements of components.
The most common design for a torsion spring is the cylindrical wound design, which consists of a coiled metal wire, in a left- or right-hand, clockwise or anti-clockwise direction and usually has legs, to which a force can be applied.
Torsional springs hold two mechanisms together and their tightness is proportional to the energy stored inside of it. Tension must be removed in order for the spring to release this stored energy.