Torsion Springs are used to apply torque or store rotational energy are commonly referred to as torsion or double torsion. Torque by definition is a force that produces rotation. A torsion spring exerts a force (torque) in a circular arc, and the arms rotate about the central axis. The stress is in bending, not in torsion.
Ammtech Spring produces a variety of Torsion Spring; types, shapes, and specific specifications