Patent ID: 8910807

Claim:
A compressible stop member for use on a crane comprising: a) a housing having a first sealed end, a second end and an internal surface comprising a first cylindrical surface having a first diameter and a second cylindrical surface having a second diameter; b) a free piston slidably contained within the housing in a sealing engagement with the first cylindrical surface of the housing; c) a compressed gas chamber in the housing between the free piston and the first sealed end; and d) a rod having a first end and a second end, and comprising a cylindrical portion with a diameter less than the second diameter of the housing and a rod support portion, the rod extending out of the second end of the housing with a sliding sealing engagement at the second end of the housing, the second end of the rod being outside said housing; e) the rod support portion being slidably contained within the housing in a sliding engagement with the internal surface of the housing, the rod support portion separating the volume between the free piston and the second end of the housing not occupied by the rod into first and second liquid chambers, the first liquid chamber comprising the volume inside the housing between the free piston and the rod support portion, and the second liquid chamber comprising the space between the rod support portion and the second end of the housing; f) wherein the rod support portion includes at least one flow channel allowing liquid to flow unimpeded, with at most a negligible pressure drop, between the first and second liquid chambers as the rod support portion slides within the housing; and g) wherein the compressible stop member further comprises a rigid stop structure selected from the group consisting of a) the second end of the rod comprising a shoulder that engages the second end of the housing so as to limit inward movement of the rod, and b) an internal stop located inside the housing past which the rod support portion cannot move in an inward direction.