A gas spring is a type of spring

Spring (device)

A spring is an elastic object used to store mechanical energy. Springs are usually made out of spring steel. Small springs can be wound from pre-hardened stock, while larger ones are made from annealed steel and hardened after fabrication...

 that, unlike a typical metal spring, uses a compressed gas

Gas

Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...

, contained in a cylinder and compressed by a piston, to exert a force

Force

In physics, a force is any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape. In other words, a force is that which can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a flexible object to deform...

. Gas springs are used in automobiles, where they are incorporated into the design of strut

Strut

A strut is a structural component designed to resist longitudinal compression. Struts provide outwards-facing support in their lengthwise direction, which can be used to keep two other components separate, performing the opposite function of a tie...

s that support the weight of hatchback

Hatchback

A Hatchback is a car body style incorporating a shared passenger and cargo volume, with rearmost accessibility via a rear third or fifth door, typically a top-hinged liftgate—and features such as fold-down rear seats to enable flexibility within the shared passenger/cargo volume. As a two-box...

 doors while they are open. They are also used in furniture, medical and aerospace applications. Much larger gas springs are found in machines that are used in industrial manufacturing (the press tooling industry), where the forces they are required to exert often range from 2500N to 400,000N (Forty tonnes).

Common applications

If the internal plunger has a diaphragm which extends to the side of the gas tube, it will cease to move once an applied force is constant and will support a weight, like a normal spring. If a fine hole exists in the plunger, however, it is termed a "slow-dampened spring" and can be used on heavy doors and windows. A gas spring designed for fast operation is termed a "quick gas spring" and is used in the manufacture of air gun

Air gun

An air gun is a rifle , pistol , or shotgun that fires projectiles by means of compressed air or other gas, in contrast to a firearm, which burns a propellant. Most air guns use metallic projectiles as ammunition. Air guns that only use plastic projectiles are classified as airsoft...

s and recoil buffer

Recoil buffer

A recoil buffer is a factory-installed or aftermarket component of firearms which serves to reduce the velocity and/or cushion the impact of recoilling parts of a firearm.-Design:...

s. Reducing the gas volume and hence increasing its internal pressure by means of a movable end stop, or allowing one tube to slide over another, can allow the characteristics of a gas spring to be adjusted during operation. The rod may be hollow by use of clever seals or may consist of multiple small-diameter rods. A small amount of oil is normally present. The gas may be introduced by a Schrader-type valve

Schrader valve

The Schrader valve is a brand of pneumatic tire valve used on virtually every motor vehicle in the world today. The Schrader company, for which it was named, was founded in 1844 by August Schrader...

, using a lip seal around the rod and forcing it to allow gas in by external overpressure or a shuttling O-ring

O-ring

An O-ring, also known as a packing, or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a disc-shaped cross-section, designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface.The O-ring...

 system. Gas springs of high pressure contain a very large amount of energy and can be used as a power pack. In emergency use the gas may be introduced via a gas generator cell

Gas generator

A gas generator usually refers to a device, often similar to a solid rocket or a liquid rocket that burns to produce large volumes of relatively cool gas, instead of maximizing the temperature and specific impulse. The low temperature allows the gas to be put to use more easily in many...

, similar to those used in airbag

Airbag

An Airbag is a vehicle safety device. It is an occupant restraint consisting of a flexible envelope designed to inflate rapidly during an automobile collision, to prevent occupants from striking interior objects such as the steering wheel or a window...

s. Gas springs are used to operate the main valve on Formula 1 racing cars.

Features

A variety of features are available from various manufacturers:

• Adjustable push-in force via a local knob or remote via a bowden wire
  Bowden cable
  A Bowden cable is a type of flexible cable used to transmit mechanical force or energy by the movement of an inner cable relative to a hollow outer cable housing...
  
  .
• Single touch release to allow full extension or the ability to lock it out.
• Extended stroke through telescoping mechanisms, usually composed of one rod and two cylinders (the smaller of the two cylinders actually acts as a second rod extending in and out of the larger cylinder).