Spiral Spring (Hairspring)

A spiral spring, commonly known as a hairspring in horology and precision instruments, is a thin, coiled spring made from specialized alloys. It functions as the restoring element in moving coil mechanisms, converting rotational displacement into linear torque while maintaining precise oscillation characteristics. This component is critical for regulating motion, storing mechanical energy, and ensuring consistent performance in devices like galvanometers, analog meters, and certain timing mechanisms.

The spiral spring operates on Hooke's law, where torque is proportional to the angular displacement. When the moving coil rotates, the spring winds or unwinds, storing potential energy. The spring's restoring force returns the coil to its neutral position, creating a balanced oscillation. Its spiral geometry provides a linear torque-angle relationship over a specific range, ensuring predictable mechanical behavior.