A gas spring is a self-contained, maintenance-free element. Gas springs are used wherever bulk or weight has to be raised or lowered steadily without much use of energy. A gas spring consists of a pressure tube – also called a cylinder – and a piston rod with piston. In addition, a seal to prevent possible loss of gas is fitted at the piston rod guide. The gas spring is filled with compressed gas – nitrogen – which provides the spring force. To cushion the end positions and lubricate the gas springs, it also contains a small quantity of hydraulic oil. The amount of oil influences the gas spring’s internal pressure. The more oil there is, the less room there is for nitrogen. Pressure is exerted on the cross-sectional area of the piston rod, which creates the extension force of the gas springs. In the unpressurised state, the piston rod is always extended. Pushing in the piston rod reduces the volume in the cylinder and the gas is compressed. This creates an increase in force (progression) for the gas spring which depends on the diameter of the piston rod and the volume of the cylinder. The piston has a small opening (nozzle) through which gas can flow, thus allowing the piston rod to move in at a defined speed. The cross-section (diameter) of this opening determines the degree of damping of a spring.
