Bellows

The term "bellows" is used by extension for a flexible bag whose volume can be changed by compression or expansion, but not used to deliver air.

For example, the light-tight (but not airtight) bag allowing the distance between the lens and film of a folding photographic camera to be varied is called a bellows.

The Old English name for "bellows" was blǽstbęl(i)g, blást-bęl(i)g 'blast-bag', 'blowing-bag'; the prefix was dropped and by the eleventh century the simple bęlg, bylg, bylig ('bag') was used.

[1] 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.

[2] The Han dynasty Chinese mechanical engineer Du Shi (d. 38) is credited with being the first to use hydraulic power on a double-action piston pumps, through a waterwheel, to operate bellows in metallurgy.

[5][6] 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.

Such pot bellows were constructed with a wide rim, so that the hide covering would transmit a maximum amount of air when pumped.

An opening near the base served to insert a pipe of perishable material whose purpose was to direct the air blast to either the furnace or crucible, and which was usually done through the mediation of a tuyère.

Bee smokers have bellows attached to the side to provide air to a slow burning fuel.

This allows for an increased rate of combustion and a temporarily higher output of smoke on command, something desirable when calming domesticated bees.