Patent ID: 7152719

Claim:
An adjustable-length compression spring, comprising a casing ( 1 ) with a central longitudinal axis ( 7 ), the casing ( 1 ) being filled with free-flowing 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 ) of the casing ( 1 ), having 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; and an operating valve ( 20 ) for connection to each other of the sectional casing chambers ( 15 , 16 ) by an actuation and overflow assembly ( 21 ), the valve ( 20 ) comprising a valve pin ( 30 ) which, from outside the casing ( 1 ), is movable into a tripped position, in which the valve pin ( 30 ) enables the actuation and overflow assembly ( 21 ) to be released, and into a shut-off position, in which the valve pin ( 30 ) shuts off the actuation and overflow assembly ( 21 ); wherein the actuation and overflow assembly ( 21 ) comprises an overflow portion with at least two overflow passages ( 25 , 29 ) connected in parallel; wherein a throttle element ( 36 ) for the actuation and overflow assembly ( 21 ) is provided, cooperating with a first overflow passage ( 25 ) of the overflow passages ( 25 , 29 ), the throttle element ( 36 ), from outside the casing ( 1 ), being movable into a position of release, in which it releases the first overflow passage ( 25 ) with the valve pin ( 30 ) in a tripped position, and the throttle element ( 36 ) being movable into a position of throttling, in which it shuts off the first overflow passage ( 25 ) with the valve pin ( 30 ) also in the tripped position; wherein at least one further overflow passage ( 29 ) of the overflow passages ( 25 , 29 ) is designed for throttled flow through the at least one further overflow passage ( 29 ) to take place in the position of throttling of the throttle element ( 36 ) with the operating valve ( 20 ) tripped; and wherein the throttle element ( 36 ) is a sealing element which is displaceable in relation to the first overflow passage ( 25 ) and which is sealed in a position of throttling inwardly towards the valve pin ( 30 ); and outwardly towards a casing-chamber portion ( 23 ) which forms a defining wall for the first overflow passage ( 25 ) as well as the at least one further overflow passage ( 29 ).