gas strut

A gas spring, also known as a gas strut or gas damper, is a type of spring that, unlike a typical mechanical spring that relies on elastic deformation, uses compressed gas contained within an enclosed cylinder. They rely on a sliding piston to pneumatically store potential energy and withstand external force applied parallel to the direction of the piston shaft (loosely analogous similarly to a bicycle pump without a gas outlet).
Gas springs are used in automobiles to support hatches, hoods, and covers. They are also used in furniture and doors, as well as in medical beds. They are used industrially in machine tool presses. Fast-acting gas springs are used in aerospace design and weapons applications, and large, extended gas springs are used in passive heave compensators, which stabilize drilling operations against waves.
Gas springs are usually implemented in one of two ways. A pneumatic suspension gas spring directly compresses a chamber of air with the piston. A hydro-pneumatic suspension gas spring instead compresses a chamber of oil linked to an accumulator in which the pressure of the oil compresses the gas. Nitrogen is a common gas in gas springs because it is inert and nonflammable.

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