The conical and volute springs, as shown in Fig., are used in special applications where a telescoping spring or a spring with a spring rate that increases with the load is desired. The conical spring, as shown in Fig(a), is wound with a uniform pitch whereas the volute springs, as shown in Fig (b), are wound in the form of a paraboloid with constant pitch and lead angles.
The springs may be made either partially or completely telescoping. In either case, the number of active coils gradually decreases. The decreasing number of coils results in an increasing spring rate. This characteristic is sometimes utilised in vibration problems where springs are used to closely coiled helical springs only.support a body that has a varying mass.
The major stresses produced in conical and volute springs are also shear stresses due to twisting.
These springs may be of helical or spiral type as shown in Fig. The helical type may be used only in applications where the load tends to wind up the spring and are used in various electrical mechanisms.
The spiral type is also used where the load tends to increase the number of coils and when made of flat strip are used in watches and clocks.The major stresses produced in torsion springs are tensile and compressive due to bending.
Laminated or leaf springs-