Gas spring, filling and sealing structure

Claim 1

A gas spring comprising: a vertical cylinder having a closed lower end; a piston slidably positioned in said cylinder; a piston rod secured to said piston and extending out or said cylinder through the upper end thereof; a rod guide secured to said upper end of said cylinder for slidingly guiding said piston rod; a stop provided in said cylinder for restricting the upward movement of said piston; a first seal mounted on said rod guide and slidingly engaging with said piston rod to sealingly close the interior of said cylinder from the exterior; at least two normally closed first passages provided in said rod guide for filling gas and, thereafter, oil into the gas spring; a second seal provided between said rod guide and said stop and sealingly and slidingly engaging with said piston rod, said second seal being sealingly displaceable in said cylinder between an uppermost position abutting said rod guide and a lowermost position abutting said stop; and a second passage formed between the inner circumference of said second seal and a portion of the outer circumference of said piston rod only when said piston rod is in the uppermost position thereof and said second seal is in said lowermost position thereof; whereby, when filling oil into a space between said first and second seals, one of said first passages is utilized to introduce oil into said space while the other first passage is utilized to exhaust gas from said space.