| 摘要 |
An adjustable turning ratio ratary positioning mechanism has rotary drive and driven members coupled by a flexible drive band, such as a sprocket chain, with oppositely movable runs between the members which are laterally displaceable during rotation of the drive member in such a way as to selectively provide the positioning mechanisms with different predetermined turning ratios, i.e., the turning angle(s) of the driven member(s) per unit turning angle of the drive member. A camera dolly steering mechanism embodying a rotary positioning mechanism according to the invention actuated by a single cam on the dolly steering shaft for selectively steering the dolly in round, crab, and conventional steering modes.
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