GASSPRING WHICH AFTER COMPRESSION HAS A TIME DELAYED RETURN TO ITS ORIGINAL LENGTH
The invention consists on the one hand of a cylinder (2) closed at its ends by means of end walls (4, 5) and on the other hand of an enclosed space (10). With a piston (3) capable of axial displacement, the cylinder (2) is divided into two sub-spaces (6, 7). The space (10) communicates with the aforementioned first sub-space (6) via a first openable and closable valve (11a). The second sub-space (7) communicates with the aforementioned first sub-space (6) via a second openable and closable valve (13a). A control device (12) actuates the openable and closable valves (11a, 13a), so that the second valve (13a) is opened when a force (F) acting upon the end of the piston rod (8) has forced the piston (3) in a direction towards the first end wall (4) and into a predetermined position. The second valve (13a) is closed again once pressure equilibrium has been achieved between the sub-spaces (6, 7). The first valve (11a) is opened for a period of sufficient duration to permit pressure equilibrium to be achieved between the second sub-space (7) and the enclosed space (10). After a predetermined period has elapsed after the force (F) acting against the end of the piston rod has ceased to be applied, the aforementioned second valve (13a) opens, when the piston (3) returns to its initial position. Once the piston (3) has reached its initial position, the first valve (11a) is opened.