Springs can be classified according to the type and nature of the forces acting on them, and can be further classified by their geometry, form, and structure. The most common form of spring is the coil spring, which is made of wire with a circular cross-section. Springs with special structures are used to absorb heavier loads or to be installed in mechanisms with small clearances.
Helical Compression Spring: This spring is designed to deflect under a compressive load. They are the most commonly used and the most common type, representing 80-90% of all springs manufactured. The geometry of the compression spring can be cylindrical, conical, convex or concave.
Conical Springs: The main feature of these springs is their nested coils. The solid length of the conical spring is designed to be approximately equal to the diameter of one or two wires. They can be used for greater deflections than cylindrical springs. Additionally, they are more resistant to buckling and lateral forces. Due to the difference in coil diameter, the spring velocity is not linear in dynamic applications. Coils with larger diameters are deflected faster. In order for the spring rate to be linear, the pitch must be varied.
Barrel and barbell/hourglass springs: These are coil springs with double cone geometry. They have the same advantages as conical springs.
Variable Pitch Cylindrical Springs: As the name suggests, these are variable pitch cylindrical springs. This allows the spring to have the variable spring rate required for dynamic applications.
Helical Tension Springs: This is a spring that can withstand a tensile load. The free length of an extension spring is nearly equal to the solid length to allow for greater deflection when stretched. The design of the tension spring is the same as that of the compression spring, but with more emphasis on the end hook design and initial tension. Tension springs make up about 10% of all manufactured springs.
Helical torsion spring: This spring has an angular force or torque that is different from the deflection of the previous two springs under linear, axial force. The torsion spring is designed to wind up the spring from the free position. This winding bends the wire section instead of the torsional model used in tension and compression springs.
Special Springs: These are non-coiled springs with geometric shapes such as wound wire, cantilever beams, discs and bars. The cross-section of the spring material is subjected to different types of stress, mostly a combination of bending and torsional stress.
Leaf springs: Leaf springs are made by laminating one (single leaf spring) or more flat springs or leaves. The layers are held together by metal clips on both ends. Leaf springs typically form an elliptical, semi-elliptical, or parabolic shape with gradually shorter leaves. They absorb and store energy through the bending of multiple planar springs and the friction between layers. They are stronger than coil springs and are used in shock absorbers for heavy vehicles.