Abstract: A gas spring which provides two stages of resistance to axial movement, by a first head and rod slidably disposed within a second rod with a head, with both of the heads subjected to pressurized gas in a common chamber within the cylinder. Preferably, a seal for each provides sealing engagement when the force of pressurized gas acts upon the seal. Hence, the seal provides sealing engagement without being axially compressed and radially expanded. The seal may be used in single stage and two stage gas springs. Desirably, a positive stop for each rod is provided, preferably as a part of the housing for its bearings and seal. Preferably, the seal is a flexible annular sealing element which when viewed in cross section is generally a C-shape, with arms constructed and arranged so that the free edges of the seal are biased into sealing engagement by pressurized gas acting on the arms.

Abstract: A gas spring with a piston rod slidably received in a cylinder which defines a chamber in which a gas is compressed when the rod is forced into the cylinder. The gas spring can be operated with either an external source of gas or as a precharged and self-contained unit by changing first and second valves assemblies either of which can be installed in the same cavity in the cylinder. If desired, a check valve can control the bleeding of gas under pressure in the cylinder back to the entrance of the cavity containing one of the valve assemblies through which the cylinder is filled with gas.

Abstract: A gas spring with a piston rod slidably received in a cylinder with a chamber which is charged with a compressed gas. A positive stop is removably received in the cylinder to limit the extent to which the rod can be extended independently of a bearing and seal assembly in the chamber in which the rod is slidably received. An end cap with a filler valve therein is removably received and releasably retained in the cylinder adjacent its other end.

Abstract: A pneumatic spring for use in absorbing an external force by compressing gaseous fluid trapped therein. The pneumatic spring includes internal valves for recharging and for relieving excessive pressure. In one form, the pneumatic spring comprises an outer housing defining an open-ended outer cylinder and an inner cylinder slidingly and sealingly positioned in the outer cylinder. The inner cylinder has a cylindrical side wall and end walls and a rod extends from the inner end wall of the outer cylinder through the inner end wall of the inner cylinder. A piston is fixed on the rod within the inner cylinder, thereby defining a first chamber between the inner end of the outer cylinder and the inner end wall on the inner cylinder and a second chamber between the piston on the rod and the outer end wall of the inner cylinder. The chambers are isolated from one another.