Leaf springs are not a new invention. They have been used since ancient Rome in one form or another, first as wooden poles and, in the 18th century, a steel plate. In 1804, Obadiah Elliot invented the first steel leaf spring that more closely resembles the leaf spring of today when he stacked steel plates and attached them to the bottom of a carriage.
One of the purposes of the leaf springs is to bear the weight of the vehicle. The semi-elliptical design helps to support the vehicle, keeping it above the frame and axle. Larger vehicles that must not only support their weight but also their heavier loads may have additional or heavy-duty leaf springs.
The leaf springs help to control the vehicle so that the tires keep in contact with the road. When the vehicle goes over a bump, the springs help to keep it from bouncing uncontrollably.
Leaf springs can help the vehicle stay in alignment as well as help with the suspension. The leaf springs absorb all the bumps and dips in the road, thus providing a more comfortable ride for the vehicle's occupants. The leaf springs also help maintain the vehicle's alignment since their very rigidity keeps the vehicle's wheels tracking straight.
