Overtravel relief assembly for a gas spring

Abstract

A gas spring for forming equipment may have a casing with an axially extending side wall, an open end, and a closed end wall with the walls defining in part a pressure chamber to receive a gas under pressure, a bearing assembly received in the casing, a piston rod slidably received in the bearing assembly for reciprocation between extended and retracted positions, a piston retainer received in the casing and separate from and normally carried by the piston rod, a deforming member in the casing adjacent its closed end wall, and configured to plastically deform the retainer when the piston rod is forced into the pressure chamber into an overtravel retracted position beyond its designed intended maximum retracted position and after such overtravel the piston rod returns to at least its extended position and the deformed retainer engages the bearing assembly and is fractured and separated from the piston rod. The gas spring may have a piston rod seal and a passage in the piston rod communicating with the pressure chamber and opening onto the piston rod at a location that do both axially inboard of engagement of the seal with the piston rod when it is in its normal extended position and generally axially outboard of and bypassing or disrupting the seal after overtravel of the piston rod and the retainer has separated from it and it has moved to a further extended position relative to its designed intended normal maximum extended position to thereby provide a path for compressed gas in the pressure chamber to pass through the passage to the exterior of the open end of the casing.