| 摘要 |
A hoist for controllably lifting, holding or lowering an object from a mobile aerial device having an articulated or extendable boom supporting a man-lifting platform. The hoist has an adjustably positioned housing and positioning plate mounted to a shaft. The shaft is secured to the boom of the mobile aerial device, in proximity to the man-lifting platform. An elongated jib with sheave at one end is supported by the housing and may be linearly positioned in relation to the hoist housing. The housing may be manually positioned in relation to the positioning plate, and the positioning plate may be rotatably positioned in relation to the mobile aerial device boom by fluid control means. A rotary fluid motor is adapted to turn a drum about the hoist shaft and controllably wind or unwind a line about the drum. The line extends from the drum about a sheave rotatably secured to one end of the jib, and is of a length sufficient to extend to the object to be moved by the hoist. Where the mobile aerial device is intended to be positioned over-center, or beyond vertical, a second sheave at the jib end to receive the line when the hoist is over-center, is provided to allow over-center hoist operation. Hoist controls are intended to be mounted near the mobile aerial platform, for ease of operation, and opposing hoist control handles may extend beyond the boom profile for use in over-center applications.
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