bellows, expansible, gas-tight chamber used to pump or store a gas. One of the simplest and most familiar types of bellows is the manual one used for providing a forced draft to a fire. The expansible chamber consists of a leather bag with pleated sides. The bag is fixed between handles in such a way that they can be used to make it expand and contract. The inlet and outlet vents are provided with valves so that air must enter through the first and leave through the second. The device thus comprises a simple air pump. One of the major uses of the bellows has been to provide a draft for fires that are used to help extract a metal from its ore. In a device such as an aneroid barometer a small bellows is filled with a known amount of gas that expands and contracts in response to changes in external pressure. This small bellows is coupled to some form of indicating or recording device. Another use of the bellows has been to provide wind for such musical instruments as the accordion and older pipe organs.

A bellows is a device for delivering pressurized air in a controlled quantity to a controlled location. Basically, a bellows is a deformable container which has an outlet nozzle. When the volume of the bellows is decreased, the air escapes through the outlet. A bellows typically also has a separate inlet and valves or flaps for ensuring that air enters only through the inlet and exits only through the outlet.

Metallurgy

Several processes, such as metallurgical iron smelting and welding, require so much heat that they could only be developed after the invention 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 Asia. (1)
• Pot bellows were used in ancient Egypt. (2)
• Tatara foot bellows from Japan.
• Accordion bellows, with the characteristic pleated sides, have been used in Europe for many centuries. (3)
• Piston bellows were developed in the middle of the 18th century in Europe (4). However, the double action piston bellows were utilised by the Han rulers in ancient China as early as the 3rd century BCE (5).
• Metal bellows were made to absorb axial movement in a dynamic condition.Often referred to as Axial Dynamics bellow types (6)

The ancient Chinese engineer Du Shi once applied water-power (waterwheel) to operate bellows of a blast furnace forging cast iron. 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.

Further applications

• Bellows are widely used in Industrial Applications such as Rod Boots, Machinery Way Covers, Lift covers and Rail Covers.

• Cuckoo clocks also use bellows
• Folding cameras such as early Polaroid models and some early Kodak Retina and Retinette cameras used bellows.

In musical instruments, the bellows is often employed as a substitute or regulator for air pressure provided by the human lungs.

The following instruments use bellows:

• Accordion, Concertina and related instruments
• Reed organ
• Pipe organ
• some varieties of Bagpipe
• Harmonium
• Portative

References

1. http://www.witzenmann.com
2. http://www.anvilfire.com/FAQs/archives/g072002d.htm .
3. http://www.archaeogate.org/egittologia/article/182/8/mersa-gawasis-red-sea-egypt-unoisiao-and-bu-2003-2004-f.html .
4. [ref. needed]
5. http://www.davistownmuseum.org/TDMtoolGlossary.htm
6. Gernet, Jacques, trans. by J. R. Foster (1972): A History of Chinese Civilization, Cambridge University Press.

See also

• sylphon for uses of metal bellows in experimental physics and engineering.

External links

• http://www.wwmag.net/blacksmith.htm for bellows used in primitive blacksmithing.
• http://www.1911encyclopedia.org/Bellows for a general discussion of bellows in metal work.