Bicycle pump

A bicycle pump is a type of positive-displacement air pump specifically designed for inflating bicycle tires. It has a connection or adapter for use with one or both of the two most common types of valves used on bicycles, Schrader or Presta. A third type of valve called the Dunlop (or Woods) valve exists, but tubes with these valves can be filled using a Presta pump.

Several basic types are available:

In its most basic form, a bicycle pump functions via a hand-operated piston. During the up-stroke, this piston draws air through a one-way valve into the pump from the outside. During the down-stroke, the piston then displaces the air from the pump into the bicycle tire. Most floor pumps, also commonly called track pumps, have a built in pressure gauge to indicate tire pressure.

Electrically-operated pumps intended to inflate car tires (as available in most service stations) can in principle be used to inflate a bicycle tire if the right type of connection is available. Some such pumps are designed to cut off before a suitable pressure (much higher for a bicycle than a car tire), and will much underinflate the tire. Others may not cut off, but deliver a high rate of flow to fill the larger car tire, with a risk of overinflating and bursting a bicycle tire unless it is stopped with split-second timing.

No day has been established as to when the first bicycle pump was invented, but it is believed to have been in or around 1887, which is when the first inflatable tire or pneumatic tire was produced by John Boyd Dunlop of Scotland. The first bicycle pump consisted of a metal cylinder that had a metal rod running down the middle of it. This would have forced the air out of the cylinder and then sucked in new air when the metal rod was pulled up again. Many modern pumps use a very similar method, while some, such as the electric pumps, use an automated pumping mechanism.

The bicycle pump compresses air. When the cylinder is compressed, air is pushed down the tube of the pump and then into the tire via the valve, which is forced open by the pressure of the air. When the handle is pulled up again, the valve shuts off automatically so that the air cannot escape from the tire, and new air is forced back into the cylinder so the process can be repeated. Some pumps have a gauge that shows the pressure of air that is forced into the tire. Once the tire is at the correct pressure, the pump valve can be removed from the tire, and the cap can be replaced on the tire valve.

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Wikipedia