The blockable gas spring is a hydropneumatic adjustable element and consists of a pressure pipe with mechanical connections for fastening, a piston rod with piston as well as a release valve. It is filled with a compressed gas, which quantitative proportion of filling dispose of the predefined inside pressure. The pressure effects on the different piston cross-section area. From this results a force which shove out the piston. This force can be fixed precisely within physical borders by the suitable choice of the filling pressure. Gas springs always consist of a cylinder and a piston movable freely in it. According to use case either both sides of the piston are filled with gas or only one side. More luxurious constructions can own one more dividing piston which separates two with gas and oil filled chambers. Therefore there is a different between oil-blocked and gas-blocked gas springs. By the easiest and most often used construction form is the whole interior filled with gas, mostly nitrogen. The piston owns a small drilling through which the gas can flow after the release valve has been activated and the measure of the damping is disposed of the drilling diameter. The smaller this drilling, the less gas can flow and the damping is higher. In the pressure pipe there is a little quantity of oil which serves the damping and lubrication. The poetry against gas loss is in the guidance of the piston rod. By shifting the piston with the help of the piston rod within the pressure pipe the volume of the nitrogen decrease there. About the small drilling in the piston the gas of the one chamber flows out into the other chamber. However, the quantity of the gas stays constantly. From this results a change of the pressure. The back set force arises from the different areas on both sides of the piston. The active cross-section of the gas on the side of the piston rod is reduced around the cross-section area of the piston rod.

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picture from Stabilus Koblenz