| 摘要 |
<p>A multisection hollow telescopic boom comprises a base section, an intermediate section and a fly section. A first elongated rotatable screw located within the boom has its base end rotatably mounted on the base end of the base section and engages a first nut which is rigidly mounted on the base end of the intermediate section. A second elongated rotatable screw located within the boom has its base end rotatably mounted on and connected to the base end of the intermediate section and engages a second nut which is rigidly mounted on the base end of the fly section. A screw drive rotates the screws to effect axial telescopic movement of the boom sections. In one embodiment the screw drive comprises a single motor for driving the first screw, a first sprocket rotatably driven by the first screw, a second sprocket for rotatably driving the second screw, and a drive chain connected between the sprockets. In another embodiment, the screw drive comprises a single motor for driving a first screw which extends into a hollow second screw, and axially slideably coupling connected between the two screws enables the first screw to rotate the second screw. In still another embodiment the screw drive comprises an individual motor for driving each screw. Screw supports are provided.</p> |
