How do constant force springs store energy?

Constant force springs are mechanical devices that store and release energy. In order to understand how they work and how they store energy, it is important to first understand what they are.

A constant force spring is a type of mechanical spring that exerts a constant force over a range of motion. Unlike traditional springs that store energy through compression or tension, constant force springs store energy through a unique mechanism that involves the interaction of two materials: spring steel and an inner hub.

The spring steel of a constant force spring is wound into a tightly coiled spiral. The inner hub, also known as the arbor, is a cylindrical core that is attached to one end of the spring. As the spring is wound around the arbor, it creates a constant torque or rotational force.

When the constant force spring is extended or compressed, the spring steel unwinds or winds around the arbor. As this occurs, the spring steel experiences a bending moment. This bending moment creates a force that resists the motion of the spring and generates a constant force.

The unique design of the constant force spring allows it to store energy in two ways. First, the spring steel stores potential energy by being wound tightly around the arbor. As the spring is extended or compressed, this potential energy is converted into kinetic energy as the spring steel unwinds or winds.

Second, the constant force spring stores energy through the bending moment created by the winding and unwinding of the spring steel. This bending moment is proportional to the distance between the arbor and the point of force, and it creates a constant force that can be used to power a variety of devices.

In order to release the energy stored by a constant force spring, the spring steel is simply unwound or wound around the arbor. This releases the potential and kinetic energy stored in the spring steel and converts it into usable energy.

Constant force springs are used in a variety of applications where a constant force is needed, such as in door closers, window counterbalances, and automotive seat belts. They are also used in medical devices such as ventilators and surgical instruments, as well as in industrial equipment such as conveyor systems and packaging machinery.

In conclusion, constant force springs store energy through the interaction of spring steel and an inner hub. The winding and unwinding of the spring steel creates a bending moment that generates a constant force, and the potential and kinetic energy stored in the spring steel can be released by simply unwinding or winding the spring. These unique devices are used in a variety of applications where a constant force is needed, and they play an important role in many industries and technologies.