Patent ID: 7201259

Claim:
An adjustable-length compression spring, having a casing ( 1 ) filled with pressure fluid; a guide and seal unit ( 6 ) which closes the casing ( 1 ) at a first end ( 5 ) ; a piston rod ( 8 ) which, through the guide and seal unit ( 6 ), is extended from, and sealed towards, the first end ( 5 ) and has an outer end ( 9 ); a piston ( 12 ) which is joined to the piston rod ( 8 ) and sealingly guided in the casing ( 1 ); a first sectional casing chamber ( 15 ) which is unilaterally defined by the piston ( 12 ) and filled with pressure fluid; a second sectional casing chamber ( 16 ) which is connectable to the first sectional casing chamber ( 15 ) and filled with pressure fluid; an operating valve ( 20 ) for connection to each other of the sectional casing chambers ( 15 , 16 ), the valve ( 20 ) comprising a valve pin ( 22 ) to be actuated from outside the casing ( 1 ) by an operating element ( 27 , 28 ), the valve pin ( 22 ) being displaceable between a position of release and a position of blocking such that in the position of release of the valve pin ( 22 ), the connection between the sectional casing chambers ( 15 , 16 ) is released; and in the position of blocking of the valve pin ( 22 ), the connection between the sectional casing chambers ( 15 , 16 ) is shut off; the adjustable-length compression spring comprising a locking mechanism ( 29 ) which is disposed in the casing ( 1 ) inside the piston rod ( 8 ), having a first locking element ( 30 ) which is in pushing connection with the operating element ( 27 , 28 ); a second locking element ( 36 ) which is in pushing connection with the valve pin ( 22 ); both of which cooperate through actuation of the first locking element ( 30 ) by the operating element ( 27 , 28 ) shifts of the second locking element ( 36 ) between a first engaged position and a second engaged position such that the valve pin ( 22 ) in a first engaged position of the second locking elements ( 36 ), is in a position of release and in a second engaged position of the second locking elements ( 36 ), is in a position of blocking.