| 摘要 |
A lazy tong or scissor-type of extendible boom structure having one end mounted on a platform. The boom structure can be extended, elevated, and/or rotated independently by drive structure mounted on the platform and a load-carrying basket is mounted on the opposite end of the boom. The boom comprises a pair of parallel lazy tongs, each comprising pairs of beams which are pivoted to one another in scissorlike fashion, the pivoted beams opposite each other on the two lazy tongs forming one "bay." Stress transmitting rigid structural cross members are fixed between the inner beams of each bay and similar cross members are nested at interference-free positions and between the outer beams of each bay to balance the torque within the pair of lazy tongs and prevent rotation of the beams and consequent twisting of the extended boom when an asymmetrical load is applied thereto, such as by an off-center load in the platform or basket or by the locating of the platform base in a non-horizontal plane.
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