Air pump
An air pump is a device for pumping air out of a closed container, whereby the internal pressure drops, or for filling a closed container with air, whereby the internal pressure increases.
The hand air pump, e.g. B. for filling bicycle tubes , is a piston pump . It consists of a cylinder and a movable piston that is moved by a rod with a handle. The piston only seals against the cylinder wall when it is compressed and pushed into the container, but not during the return stroke, so that a new filling can get into the cylinder from the outside, while the return flow from the container into the pump cylinder is prevented by a valve that is either on the container (bicycle tube) or on the lower end of the pump cylinder (air pump for balls).
A machine-operated air pump is called a vacuum pump , compressor or compressor.
history
Originally and up until the 19th century, the word air pump primarily referred to a pump with which air could be pumped out of a closed container and thus an approximate vacuum could be generated. The piston vacuum air pump was invented in 1649 by Otto von Guericke , the mayor of Magdeburg and who became famous for his experiments on air pressure with the Magdeburg hemispheres . Robert Boyle improved the air pump together with Robert Hooke in 1659 . Very important physical knowledge was gained through the air pump , including the proof of the existence of the vacuum, Boyle-Mariotte's law about gases , that sound cannot propagate in a vacuum and that in free fall all bodies fall to the ground at the same speed, if you can neglect the air resistance.
The use of air pumps to fill elastic, airtight containers such as balls and pneumatic tires with compressed air only became of practical importance later. The first pneumatic bicycle tire was developed by John Boyd Dunlop in 1888 .
Bicycle pump
A bicycle pump is specifically used to fill bicycle tires with air. A basic distinction can be made between hand, foot and floor pumps. Hand pumps can be used to inflate tires to a pressure of around 5 bar , high-quality floor pumps reach more than 12 bar. The tire pressure of a bicycle is significantly higher than that of a car tire.
Since there are different bicycle valves on the market, care must be taken to ensure that the air pump is compatible. However, some products have multiple connections or can be equipped with an adapter .
The pressure level offered by compressors at petrol stations is more than sufficient for everyday bikes and can be easily used with adapters or car valves. On the other hand, the pressure is not sufficient for the very thin high-pressure bicycle tires.
safety
In a standing air pump, which can also inflate Dunlop hose valves, much higher forces act than in hand air pumps, with which mostly only Dunlop valve quick valves can be inflated. In the case of inferior standing air pumps, this can lead to the handle breaking in the middle, after which the piston rod can become a dangerous projectile.
Another source of error is the base of the standing air pumps, which in some cases also represents a separate component with a base that is too short and which is only connected to the cylinder with an industrial adhesive.
literature
- Alto Brachner (Ed.) History of Vacuum Pumps , Munich: Deutsches Museum, 2002, ISBN 978-3-924183-82-0 (previously: 3924183821) and there respectively named Prim.lit.
- Michael Gressmann, Franz Beck, Rüdiger Bellersheim: specialist knowledge of bicycle technology. 1st edition. Verlag Europa-Lehrmittel, Haan-Gruiten 2006, ISBN 3-8085-2291-7 .
- Fritz Winkler, Siegfried Rauch: Bicycle technology repair, construction, production. 10th edition. BVA Bielefelder Verlagsanstalt, Bielefeld 1999, ISBN 3-87073-131-1 .
See also
- Work on inflating a bicycle tire
- Enthalpy (here: warming due to the displacement work that is carried out when inflating a tire)
Individual evidence
- ↑ See for example Brockhaus 1809 air pump