| 摘要 |
The frame (2), carrying e.g. a high-powered lighting installation, hangs on e.g. 3 cables (14), which pass over pulleys (12,13) running freely on horizontal axles in a mast-head structure (4), and extend down within the hollow mast (3) to a counterweight. The equipment thus mounted can be easily lowered to ground level and later, after maintenance or other work, returned to mast-head level. The mast-head structure, bolted (18) to an end-plate (17) on the mast top, comprise 3 equally spaced radial arms (5), constructed as deep narrow boxes, containing the pulleys, their side plates supporting the pulley axles (10,11). As the frame, rising, nears the mast-head, rollers (19) at the outer end of each arm pass into guide channels (20) bolted to the frame's circular main member (22), while a latching roller (7), on a vertical resilient finger (6) in the frame engages in a gate (8) at the side of each arm. The cables terminate at the foot of each channel. Channels, open inwardly, are interconnected at the foot (26) by spacers (24). Their flared lips (21) ease the rising frame into correct alignment. Each latching roller enters its gate along an inward face, springing back into a V-recess to transfer the frame's weight to the mast-head. Slightly raising the frame further allows the roller to escape by a separate exit, then descend an outer face (30,29) as the frame is lowered.
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