Patent ID: 7891508

Claim:
A crane comprising: a vertical post including a post bearing surface forming at least a partial arc about a vertical axis of the vertical post; a superstructure pivotal about the vertical post and including a boom foot having a pivot point; a boom extending from the boom foot and pivotable in a vertical plane about the pivot point in response to one or more lines extending between the boom and a swivel-post head near a top of the vertical post; a single roller chain encompassing at least a segment of the post bearing surface and comprising: a plurality of rollers arranged in a pivotally-linked sequence, each roller including a rotational axis generally parallel to the vertical axis of the vertical post and a roller surface in rolling contact with the post bearing surface, wherein the rollers are distributed with equal spacing on an arc along the post bearing surface with at least 180 degrees between a first roller and a last roller; a first anchor coupled to the crane superstructure and operably, pivotally-linked to the first roller; and a second anchor coupled to the crane superstructure and operably, pivotally-linked to the last roller; and the first and second anchors being positioned to make the arc of the roller chain substantially symmetrical with respect to the vertical plane of boom motion and to tension the rollers against the post-bearing surface, whereby the pivoting action of the rollers maintains substantially equal distribution of radial loads from the boom across all rollers in the roller chain.