Patent ID: 7401769

Claim:
A method of manufacturing a gas spring comprising the steps of: a) forming a piston rod assembly comprising the steps of: i) providing a piston rod with a piston in a leading end portion, which is adapted to be slidably inserted into a cylinder, ii) providing a first seal member and a second seal member spaced in an axial direction, by inserting a rebound member, fitting the first seal member in close contact with an outer periphery of the piston rod, fitting an annular space member in close contact via a backup ring with the outer periphery of the piston rod, fitting the second seal member in close contact with the outer periphery of the piston rod, and inserting a rod guide which guides the piston rod, to the outer periphery of the piston rod and against a surface of the piston in accordance with this order from a side of the piston; fitting, to the outer periphery of the piston rod, in order against the piston, a rebound member, a first seal member in close contact with the piston rod, an annular space member having a backup ring in close contact with the piston rod, a second seal member in close contact with the piston rod, and a rod guide, the rebound member being in direct contact with the piston, iii) connecting a divided lubricant injection jig between the second seal member and the annular space member; and iv) injecting a lubricant in an annular chamber defined among the first seal member, the annular space member and the second seal member, in the outer periphery of the piston rod, b) providing at an opening portion of an inner portion of a cylinder the piston rod assembly in which a lubricant is previously injected, c) charging a pressurized gas into the cylinder from an opening portion of the cylinder under a sealed state, d) thereafter pressing the rod guide, thereby inserting the piston rod assembly into the cylinder from the opening portion of the cylinder such that the first seal member is in close contact with an outer periphery of the piston rod and an inner periphery of the cylinder, the annular space member is adjacent to the inner periphery of the cylinder, and the second seal member is in close contact with the outer periphery of the piston rod and the inner periphery of the cylinder, and e) fixing the rod guide to the cylinder by caulking the rod guide to the cylinder.