Power Springs and Spring Motors Information
Power springs and spring motors are rotational-drive springs that are wound tightly and mounted on an arbor.
Typically, power springs and spring motors are used in applications such as:
- retractable reels
- tape measures
- retracting seat belts
Some power springs and spring motors are used in wrist watches, vehicle suspensions, electrical switches, bows, or galvanometers. Other power springs and spring motors are used in medical or military applications. Clock springs are commonly available. Very heavy springs are used in industrial drives to provide large torque.
A spring is a flexible elastic object used to store mechanical energy. Often, springs are made of hardened steel. Most power springs and spring motors are produced by tightly winding tempered spring material on an arbor and attaching the free end to a metal or plastic case. The spring’s natural tendency to expand imparts a momentum to either the arbor or case, producing usable torque. The torque generated is cumulative and increases the force as the spring is wound tighter and decreases as it unwinds. Power springs and spring motors work inside a housing and exert torsional force against either a central shaft or the housing itself.
Power springs and spring motors are made from a variety of different materials, depending on their application. Smaller springs can be made from beryllium copper or similar alloys. Larger springs are made from a high-carbon steel called blue clock for its color. A constant-torque power spring or spring motor attaches the free end of a spring to a larger drum. The spring is wound around the drum in either the same direction or in the reverse direction. Clock springs are made from flat stock and coiled like a snail shell, with each coil nesting inside the next larger one. The energy storage capacity (ESC) of a spring is determined by bending (deforming) the material in a spring. Many power springs and spring motors are shipped in customer-designed retainers for direct insertion into the customer’s product, or as simple retaining rings for transfer to the customer’s housing.