FUNDAMENTAL CONSIDERATIONS

Types of Springs

Nearly every physical body acts as a spring of some kind. For example, even the largest beam deflects and then returns to its initial position when the slightest load is applied and then removed. However, a mechanical spring is designed so that it will deflect, relatively, a considerable amount when a load is applied, store the energy that has been used to deflect it, and then release this energy as it returns to its initial position. Numerous types of springs have been designed to perform this fundamental function either by exerting a push, pull, torque, or a combination of these actions. In order to facilitate a discussion of the special design considerations, the many kinds of springs are grouped into general types according to the way they exert force and store energy.

Compression, extension, and torsion springs are named by the manner in which they exert force and store energy. The many other types of springs, including flat springs, are usually named only by their shape or application.

Compression Springs

Helical coil compression springs are compressed along their axes of winding and exert a pushing force. The ends are usually flat, though they may be of special design to facilitate mounting.

Extension Springs

Helical coil extension springs are stretched along their axes of winding and exert a pulling force. They must have a hook or some other arrangement for attachment and are made in a variety of end styles to ful¬fill this requirement.

Torsion Springs

Helical coil torsion springs are twisted about their axes of winding and exert a torque. They may be provided with various style arms for different applications.

Double torsion springs consist of one right hand and one left hand torsion spring connected together. Each hand exerts a separate torque with the total being the sum of both hands.

Wire forms

There is an infinite variety of wire forms. The shape and function of wire forms are dependent on their mating parts.

Flat Springs

Flat springs include a large group of springs made from flat or strip material. They are generally classified as either cantilever or elliptical and are made for a wide variety of applications.

Miscellaneous Springs

There are many other types of springs that do not fall into any of the above categories. Frequently used types include:

Energy

The design of springs is based on the consideration of a large number of factors, three of which are: load, deflection and stress. The load and the corresponding deflection represent the rate of change of energy absorption. The stress is a measure of the distribution of the applied force.

For helical coil springs, the volume of active material is the same for any combination of load and deflection, providing the stress and type of cross section remain constant. For compression and extension springs, this relationship is given by:

V = K1 P F G
  2 S2

V - Volume of active wire
P - Load
F - Linear Deflection
G - Modulus of Elasticity in torsion
S - Stress
k1 - Constant: for round wire K1 = 4;
for square wire K1 = 6.5;
for rectangular wire, K1 is variable;