Several processes, such as metallurgical iron
smelting and
welding, require so much heat that they could only be developed after the invention, in
antiquity, of the bellows. The bellows are used to deliver additional air to the fuel, raising the rate of combustion and therefore the heat output. Various kinds of bellows are used in
metallurgy: • Box bellows were and are traditionally used in East Asia. • Pot bellows were used in ancient Egypt. •
Tatara foot bellows from Japan. •
Accordion bellows, with the characteristic pleated sides, have been used in Europe for many centuries. • Piston bellows developed in Southeast Asia (probably by the
Austronesian peoples) using the principles of the similarly indigenous
fire piston. It led to the independent development of
bronze and
iron metallurgy in
Southeast Asia. They were present in various Southeast Asian cultures, and the technology was transported to
Madagascar via the
Austronesian expansion. :*The technology was later adopted and refined by the Han Chinese into the double-action piston bellows, replacing the native Chinese ox hide pot or drum bellows completely. The
ancient Greeks,
ancient Romans, and other civilizations used bellows in
bloomery furnaces producing
wrought iron. Bellows are also used to send pressurized air in a controlled manner in a fired heater. In modern industry, reciprocating bellows are usually replaced with motorized blowers.
Double-acting piston bellows Double-acting piston bellows are a type of bellows used by
blacksmiths and
smelters to increase the air flow going into the forge, with the property that air is blown out on both strokes of the handle (in contrast to simpler and more common bellows that blow air when the stroke is in one direction and refill the bellows in the other direction). These bellows blow a more constant, and thus stronger, blast than simple bellows. Such bellows existed in
China at least since the 5th century BC, when it was invented, and had reached Europe by the 16th century. In 240 BC, The ancient Greek inventor
Ctesibius of Alexandria independently invented a double-action piston bellow used to lift water from one level to another. A piston is enclosed in a rectangular box with a handle coming out one side. The
piston edges are covered with feathers, fur, or soft paper to ensure that it is
airtight and
lubricated. As the piston is pulled, air enters from the far side and the air in the near chamber is compressed and forced into a side chamber, where it flows through the nozzle. Then as it is pushed air enters from the near side and the air in the far chamber flows through the same nozzle.
Double-lung accordion bellows These have three leaves. The middle leaf is fixed in place. The bottom leaf is moved up and down. The top leaf can move freely and has a weight on it. The bottom and the middle leaves contain valves, the top one does not. Only the top lung is connected to the spout. When the bottom leaf is moved up, air is pumped from the bottom lung into the top lung. At the same time air is leaving the bellows from the top lung through the spout, but at a slower rate. This inflates the top lung. Next the bottom leaf is moved down to pull fresh air into the bellows. While this happens the weight on the top leaf pushes it down, so air keeps leaving through the spout. This design does not increase the amount of air flow going into the forge, but provides a more constant air flow compared to a simple bellows. It also provides more even air flow than two simple bellows pumped alternately or one double-acting piston bellows. ==Primitive bellows==