It is essential that a designer select the optimum spring configuration to perform an intended function. A three-step procedure has been developed for this task:
1. Define the primary spring function in terms of push, pull, twist or energy storage.
2. Review various alternative configurations and select one or two best candidates.
3. Review candidate configurations with respect to cost and special considerations.
Having defined primary spring function as either push, pull or twist, the next step is to review all different types of springs and configurations that perform this function and select the one that meets space requirements most economically.
Helical compression springs, spring washers, volute springs and beam springs all perform a push function. For large deflections, helical compression springs are most commonly chosen. For small deflections, spring washers are most common. Volute springs have high damping capacity and good resistance to buckling, but are not common because of relatively high manufacturing costs.
Beam springs are produced in a wide variety of shapes and can push or pull. Frequently, beam springs are required for functions in addition to the spring function, and sometimes are an integral element of a larger part.
Helical torsion and spiral spring configurations perform the twist function. Helical torsion springs are often used as a counterbalance for doors, lids or other mechanisms that rotate on a shaft. Spiral hairsprings have a low hysteries and are used in instruments and watches.
Brush springs received their name from their primary application of holding brushes against commutators in electric motors.
Power springs are often called clock or motor springs and are used to store energy for clocks, toys and other devices. Prestressed power springs are a special type of power spring that has a very high-energy storage capacity and is most commonly used on refractors for seat belts. Constant force springs provide an essentially constant torque over many revolutions.
Extension springs, drawbar spring assemblies and constant force springs, with helical extension springs being most common, perform the pull function. Drawbar spring assemblies are useful when a fixed stop is required. Constant force springs are similar to power springs; however, they are loaded by pull rather than twist.
Retaining rings and garter springs were especially developed to perform either push or pull. Retaining rings retain or locate parts in bearings and on shafts.
Garter springs are used primarily in oil seals.
Often a spring design function is expressed in terms of energy storage capacity. In machines, springs are frequently used to store kinetic energy from moving components during deceleration and release this energy during acceleration to reduce peak loads. Spring motors are used to power clocks, toys and many other mechanical devices. Torsion springs are used in window shades and garage doors because of their ability to store energy.