| 摘要 |
<p>A method and apparatus for controlling the angle of a pivoted, pendant supported extensible boom (12) and the mast-boom angle between working positions and a transport position. The structure for controlling the angle includes a wire rope (62) driven by a whinch (24) and trained over a boom supporting hoist (68) and over a pendant take-up hoist (10) which includes a floating sheave assembly (72) connected to an extensible portion (34) of the boom (12) by a fixed length pendant (80). Another fixed length pendant (48) determines the most-boom angle when the boom (12) is in working position, and a floating sheave stop (82) is pivoted to the mast (44) in position to cradle and/or abut a portion (76) of the floating sheave assembly (72) for enabling completed control of the mast (44) when moved between its transport position and working positions relative to the boom (12). </p> |
