Patent ID: 7540362

Claim:
An adjustable-length gas spring, comprising a casing ( 1 ) which has a central longitudinal axis ( 2 ) and is filled with a liquid pressure fluid; a guide and seal unit ( 10 ) which closes the casing ( 1 ) at a first end; a piston rod ( 8 ) for sealed guidance through the guide and seal unit ( 10 ) out of the first end of the casing ( 1 ); a piston ( 9 ) for sealed guidance in the casing ( 1 ), the piston ( 9 ) being joined to the piston rod ( 8 ); a first divisional interior chamber ( 7 b ) which is formed between the piston ( 9 ) and the guide and seal unit ( 10 ); a second divisional interior chamber ( 7 a ) which is defined by the piston ( 9 ) and turned away from the first divisional interior chamber ( 7 b ); an adjusting valve ( 37 ) which is disposed in the piston ( 9 ) and interconnects the first and second divisional interior chamber ( 7 a , 7 b ), having a valve control pin ( 20 ) which is displaceable in a direction of the central longitudinal axis ( 2 ), a valve tray ( 21 ) which is mounted on the valve control pin ( 20 ), a first sealing seat ( 24 ), and a first sealing contact surface which cooperates with the first sealing seat ( 24 ), the first sealing seat ( 24 ) and the first sealing contact surface being liftable off each other by means of the valve control pin ( 20 ); a traction valve ( 38 ), which is disposed on the piston ( 9 ), for interconnection of the first and second divisional interior chamber ( 7 a , 7 b ) when tractive force acts between the piston rod ( 8 ) and the casing ( 1 ), the traction valve ( 38 ) having a second sealing seat ( 32 ), and a second sealing contact surface that cooperates with the second sealing seat ( 32 ), the second sealing seat ( 32 ) and the second sealing contact surface, upon increase of pressure in the first divisional interior chamber ( 7 b ), being liftable off each other while the traction valve ( 38 ) opens; and the adjusting valve ( 37 ) and the traction valve ( 38 ) having a joint sliding bush ( 26 ) which is guided for displacement on the valve control pin ( 20 ) in the direction of the central longitudinal axis ( 2 ) and bears either the first or second sealing contact surface or the first or second sealing seat ( 24 , 32 ).