Bellows
Bellows or pair of bellows is a device constructed to furnish a strong blast of air or to lift objects. The simplest type consists essentially of a flexible bag comprising a pair of rigid boards with handles joined by flexible leather sides enclosing an approximately airtight cavity which can be expanded and contracted by operating the handles, and fitted with a valve allowing air to fill the cavity when expanded, and with a tube through which the air is forced out in a stream when the cavity is compressed.It has many applications, in particular blowing on a fire to supply it with air.
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 thelens and film of a folding photographic camera to be varied is called a bellows.
Applications
- Bellows are widely used in industrial and mechanical applications such as rod boots, machinery way covers, lift covers and rail covers to protect rods, bearings and sealings from dirt.
- Bellows are widely used on articulated buses and trams, to cover the joint where the vehicle bends.
- Bellows are an essential part of anesthesia machines.
- Bellows tubing, a type of lightweight, flexible, extensible tubing may be used for delivery of gas or air at near-ambient pressure, as in early aqua-lung designs.
- Cuckoo clocks use bellows to blow air through their pipes and imitate the call of the Common Cuckoo bird.
- Folding and view cameras use bellows to exclude light while allowing the lens to be moved relative to the film plane for focusing and, mainly in view cameras, to allow the lens to slide and tilt to control the image.
- Musical instruments may employ bellows as a substitute or regulator for air pressure provided by the human lungs.
- Piping expansion joint: In this application, bellows are formed in series to absorb thermal movement and vibration in piping systems that transport high temperature media such as exhaust gases or steam.