Compressible stop member for use on a crane

A compressible stop member mounted on a crane, the crane comprising a column member and the compressible stop member being selected from the group consisting of a boom stop, a jib stop, a mast stop and strut stop, the at least one compressible stop member 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 between the first and second liquid chambers as the rod support portion slides within the housing;
• and
• g) wherein one of the sealed end of the housing and the second end of the rod comprises a column member engagement surface for engaging the column member and the other of the sealed end of the housing and second end of the rod is pivotally attached to the crane.

A lift crane comprising:

• a) a carbody;
• b) ground engaging members elevating the carbody off the ground;
• c) a rotating bed rotatably connected to the carbody;
• d) a boom pivotally mounted on the rotating bed;
• and
• e) at least one compressible stop member selected from the group consisting of a boom stop, a jib stop, a mast stop and a strut stop, the at least one compressible stop member comprising:
• i) 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;
• ii) a free piston slidably contained within the housing in a sealing engagement with the first cylindrical surface of the housing;
• iii) a compressed gas chamber in the housing between the free piston and the first sealed end;
• and
• iv) 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;
• v) 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;
• vi) wherein the rod support portion includes at least one flow channel allowing liquid to flow unimpeded between the first and second liquid chambers as the rod support portion slides within the housing;
• and
• vii) 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, and b) an internal stop located inside the housing past which the rod support portion cannot move in an inward direction.

A method of stopping a column member that is pivotally mounted on a lift crane from tipping over backward comprising:

• a) providing at least one compressible stop member selected from the group consisting of a boom stop, a jib stop, a mast stop, and a strut stop, the at least one compressible stop member comprising:
• i) 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;
• ii) a free piston slidably contained within the housing in a sealing engagement with the first cylindrical surface of the housing;
• iii) a compressed gas chamber in the housing between the free piston and the first sealed end;
• and
• iv) 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;
• v) 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;
• vi) wherein the rod support portion includes at least one flow channel allowing liquid to flow unimpeded between the first and second liquid chambers as the rod support portion slides within the housing;
• and
• vii) 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, and b) an internal stop located inside the housing past which the rod support portion cannot move in an inward direction;
• and
• b) attaching the at least one compressible stop member to the crane with a pivotal connection and positioned so that the compressible stop member will engage the column member when the column member reaches a first angle;
• c) wherein movement of the column member from said first angle to a second steeper angle causes the rod to be pushed into the housing, thereby forcing the rod support portion toward the free piston, with liquid flowing from the first liquid chamber into the second liquid chamber as the rod travels, creating an increased volume in the second liquid chamber but a decreased volume in the first liquid chamber and a commensurate increase in pressure in the gas chamber and on the rod support portion, thereby impeding the movement of the column member towards the second steeper angle, and when the column member reaches a third angle greater than the second angle, the rigid stop structure is able to prevent any further increase in the column member angle.