Adjustable-length gas spring

An adjustable length gas spring, comprising

• a housing (1), which has a central longitudinal axis (7) and is filled with a free-flowing fluid;
• a guide and seal unit (6), which closes a first end (5) of the housing (1);
• a piston rod (8), which has an outer end (9) and is extended from, and sealed towards, the first end (5) of the housing (1) by the guide and seal unit (6);
• a piston (12), which is connected with the piston rod (8) and sealingly guided in the housing (1);
• a first partial volume (15), which is formed between the piston (12) and the guide and seal unit (6);
• a second partial volume (16), which is defined by the piston (12) and turned away from the first partial volume (15);
• and
• a valve (20) for interconnection of the partial volumes (15, 16), which has a valve pin (24) which is actuated from outside the housing (1) and which, when pushed in a valve opening direction (40) in the sense of the central longitudinal axis (7), is moved into an opening position of the valve (20) and into a closing position by pressure of the fluid counter to the valve opening direction (40);
• wherein, when a force that acts between the piston rod (8) and the housing (1) in a push-in direction (43) of the piston rod (8) exceeds a given threshold, the valve pin (24) is displaceable from the closing position counter to the valve opening direction (40) and against a spring unit (34) into a position of opening by overload.