Abstract: A gas spring includes a vertical cylinder, a piston rod extending out of the cylinder through the upper end thereof, a rod guide provided on the upper end of the cylinder for guiding the piston rod, a first seal mounted on the rod guide, a partition wall provided in the cylinder to partition the interior thereof into an upper oil chamber and a lower gas chamber, and a second seal cooperating with the partition wall and slidingly engaging with the piston rod. At least two normally closed first passages are provided in the rod guide and communicate the interior of the cylinder with the outside when filling gas and in filling oil into the cylinder, and a second passage is provided to communicate the gas chamber with the oil chamber when filling gas into the gas chamber.

Abstract: A gas spring comprises a cylindrical outer sheath having a stopper holding structure on the inner surface, a rod and piston unit slidably received in the outer sheath, a rod guide and a packing sealably fitted in the outer sheath, and a stopper freely received in the outer sheath for limiting the upward movement of the piston and having engaging structure on the outer surface to engage on the stopper holding structure to thereby hold the stopper in position in the outer sheath.

Abstract: A method for filling gas into a cylindrical container having a rod slidably extending from one end thereof. The method comprises forming passage means in the rod at a position adjacent to the inner end thereof, projecting the rod outwardly to its maximum extending position so as to form a gas filling passage by said passage means across an annular seal member which normally engages the rod sealingly and slidably, filling high pressure gas into the container through the gas filling passage, and moving the rod inwardly relative to the seal member to close the gas filling passage.

Abstract: A locking device in a gas spring including a cylinder, a free piston slidably disposed in the cylinder for dividing the interior of the cylinder into a gas chamber and an oil chamber, and a piston slidably disposed in the oil chamber and having a piston rod extending outwardly from the cylinder, the locking device comprises a free piston rod secured to the free piston and projecting outwardly from the cylinder, and means secured to the cylinder for engaging with and controlling the movement of the free piston rod relative to the cylinder.