Length-adjustable gas spring

Claim 1

A continuously length-adjustable compressed gas-filled spring, such as for height adjustment of chair seats, table tops or the like comprising an outer cylinder constituting a housing; an inner cylinder coaxially disposed in said outer cylinder, and defining an annular chamber therebetween; a piston mounted coaxially displaceably within said inner cylinder, said piston sealingly contacting the inner wall of said inner cylinder to prevent leakage of said gas across said piston between a first chamber on one side of said piston and a second chamber on the other side of said piston, said piston being connected to a piston rod extending through one end of the housing in a gas-tight manner through a first sealing plug at one end of said cylinders, a second sealing plug to seal the two cylinders at the opposite end in a gas-tight manner; means to provide communication between said first and second chambers separated in a gas-tight manner by the piston on the piston rod, said means comprising a valve including a valve push rod serving as a valve release pin and extending through the other end of said housing in a gas-tight manner through said second sealing plug, a first bypass channel located in the vicinity of said second sealing plug which is in the vicinity of said valve push rod, a second bypass channel located in the vicinity of said first sealing plug, said valve comprising a piston sealing element coaxially displaceably mounted and guided in a gas-tight manner in said inner cylinder on said valve push rod; a bypass depression in the inner wall of said inner cylinder, whereby said valve is opened by moving said piston sealing element axially adjacent said bypass depression to provide gas flow communication between said first and second chambers through said bypass depression, said first and second bypass channels and said annular chamber, and said valve is closed when said piston sealing element is in a position axially spaced from said bypass depression to close said gas flow communication between said first and second chambers.