| 摘要 |
<p>A pendant supported extensible boom is disclosed having the boom and a live mast pivoted to a base about an axis near the lowermost surface of the boom for providing a stowed mast-boom angle of about 10.degree., and a fixed length pendant is provided to maintain a predetermined mast-boom working angle. A live pendant is trained over a winch, a boom supporting hoist, and a pendant take up hoist connected between the mast and an outer end portion of the boom. Driving the winch to haul in pendant controllably raised the mast to its mast-boom working angle and then raises the boom to its desired working angle. When extending or retracting the boom, the boom working angle is maintained constant by paying out pendant from the winch and drawing in pendant from the winch, respectively. The boom and mast are controllably returned to a stowed position by paying out line from the boom supporting hoist and pendant take-up hoist.</p> |
