TYPES OF SPRINGS

What are the different types of springs?

Types of springs can be differentiated according to the direction and the nature of the force exerted by the spring when it is deflected.

Table 1

Table 1 lists several kinds of springs classified as push, pull, radial, and torsion.  

Types of springs
Figure 1: Types of springs

Figure 1 shows several typical designs.  

Round wires are used to make helical compression springs, wrapped into a straight, constant pitch between adjacent coils for cylindrical forms. There might be use of square or rectangular wire. 

Appearance of helical compression springs showing end treatments
Figure 2: Appearance of helical compression springs
showing end treatments

Four practical end configurations are shown in Figure 2.  

Without an applied load, the spring’s length is called the free length.  

When a compression force is applied, the coils are pressed more closely together until they all touch, at which time the length is the minimum possible called the solid length.  

Deflection is increased when an increasing force is applied on the spring which tends to compress it. The most widely used springs are straight & cylindrical helical compression springs. 

Also shown in Figure 1 are the conical, barrel, hourglass, and variable-pitch types.  

Helical extension springs appear to be similar to compression springs, having a series of coils wrapped into a cylindrical form.  

Under no load condition, the coils either touch or are closely spaced in extension springs. 

Then as the external tensile load is applied, the coils separate.  

End configurations for extension springs
Figure 3: End configurations for extension springs

Figure 3 shows several end configurations for extension springs.  

Two looped wire devices are inserted inside the springs which is present in the drawbar spring as shown in figure 3. 

Pulling the loops will exert a force when the spring is in compression state for such designs. 

Due to this a definite stop is induced when the compression spring is compressed to its solid height. 

A torsion spring, as the name implies, is used to exert a torque as the spring is deflected by rotation about its axis.  

The common spring-action clothespin uses a torsion spring to provide the gripping action.  

The purpose of torsion springs is typically used to rotate a door for opening, closing or to counterbalance the lid of a container.  

Some timers and other controls use torsion springs to actuate switch contacts or to produce similar actions.  

Push or pull forces can be exerted by torsion springs if one end of the spring is attached to the member to be actuated.

One or more flat strips of brass, steel, bronze or other materials are loaded as cantilevers or simple beams. 

If they are deflected from their free condition then they can provide a pull or push force. 

Large forces can be exerted within a small space by leaf springs.  

By tailoring the geometry of the leaves and by nesting leaves of different dimensions, the designer can achieve special force-deflection characteristics.  

Principal of stress and deflection analysis of beams is used to design the leaf springs. 

The shape of Belleville spring is mostly shallow, conical disk with a central hole. 

Belleville spring is sometimes called as a Belleville washer as it resembles a flat washer. 

A very high spring rate or spring force can be developed in a small axial space with such springs.  

Variety of load deflection characteristics can be obtained by the designer, by varying the height of the cone with respect to the thickness of the disk. 

Also, nesting several springs face-to-face or back-to-back provides numerous spring rates. Garter springs are coiled wires formed into a continuous ring shape so that they exert a radial force around the periphery of the object to which they are applied.  

With different designs inward or outward forces can be obtained. 

Application of inward force on garter spring is similar to that of a rubber band, and the spring action is similar to extension spring. 

Springs tend to form itself in a strip format when a constant force is applied. 

Power springs, sometimes called motor or clock springs, are made from flat spring steel stock, wound into a spiral shape.  

A torque is exerted by the spring as it tends to unwrap the spiral.  

Figure 3 shows a spring motor made from a constant-force spring.  

A bar loaded with tension is known as a torsion bar. 

Other cross-sectional shapes can be used, and special care must be exercised at the points of attachment. 

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