A clockwork spring, also known as a (coil) spring, is a spring with a spiral in a plane. A spring is a spring in which the material is wound into a flat spiral shape. One end of the spring is fixed and the other end acts as a torque. The rear material is subject to a bending moment and produces bending elastic deformation, so the spring twists in its own plane. The size of its deformation angle is proportional to the torque. It has high torsion force and multi-angle torsion moment, so it is used in mechanisms that perform work for a long time. It has the characteristics of not easy to fatigue. Its use is similar to a torsion spring. It is generally used in tape measures, car starter motors, wire storage boxes, etc.