| 摘要 |
A ring supported, self-propelled truck crane and method of operation is disclosed wherein a boom is mounted on the chassis for pivotal movement only about a horizontal axis. The chassis is driven into an incomplete segmented ring set up at a working site with rollers on end portions of the chassis projecting downwardly and overlying the ring when the ring opening is closed by adding an additional segment thereto. The ring is then elevated to lift the wheels of the chassis completely off the ground and drive means interconnect the ring and the chassis to rotate the chassis about the vertical axis of the ring. Flanged rollers journaled on the chassis engage the ring to center the chassis on the ring and to rotatably interconnect and support the ring on the chassis for transportation therewith to the next site when the ring and chassis are lowered for support entirely upon the wheels of the truck crane. The preferable embodiment includes a front wheel drive permitting working of the crane on a small diameter ring when retracted and permitting extension of the crane's wheel base during transport to comply with road weight/wheel base laws.
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