Patent ID: 7467774

Claim:
An adjustable-height chair column, comprising an upright tube ( 1 ) with a central longitudinal axis ( 3 ); a gas spring ( 4 ), which is disposed in the upright tube ( 1 ) coaxially of the central longitudinal axis ( 3 ), and which comprises a casing ( 6 ) that is filled with pressure fluid and displaceable in a direction of the central longitudinal axis ( 3 ) into an extended position, a piston rod ( 12 ) that is fixed in the upright tube ( 1 ), a piston ( 14 ) that is mounted on the piston rod ( 12 ), dividing the casing into a first sectional casing chamber ( 11 ) and a second sectional casing chamber ( 15 ) the piston rod ( 12 ) passes through, and a valve ( 9 , 9 ′, 9 ″) for interconnection of the first and second sectional chamber ( 11 , 15 ) which comprises a valve gate ( 29 , 29 ′) with a valve throat ( 33 , 33 ′) that is coaxial of the central longitudinal axis ( 3 ), a valve pin ( 32 , 32 ′, 32 ″) that is disposed in the valve throat ( 33 , 33 ′) for displacement in a direction towards the first sectional casing chamber ( 11 ) into a position of opening, having a blocking element ( 36 , 36 ′, 36 ″), and a seal ( 41 , 50 ) that, in a shut-off condition of the valve ( 9 , 9 ′, 9 ″) and upon load on the casing ( 6 ) in relation to the upright tube ( 1 ), seals between the blocking element ( 36 , 36 ′, 36 ″) and the valve body ( 29 , 29 ′); wherein the valve ( 9 , 9 ′, 9 ″) is designed for opening upon relief of the casing ( 6 ) in relation to the upright tube ( 1 ); wherein a mechanism of reverse rotation ( 23 ) is provided between the upright tube ( 1 ) and the casing ( 6 ).