| 摘要 |
A rotational control apparatus (10) includes a first rotatable assembly (20) and a second rotatable assembly (96). The first assembly (20) is rotatably mounted to a first support mount (12). The second assembly (96) is rotatably mounted to the first assembly (20) and is axially moveable relative to the first assembly (20). The first and second assemblies (20, 96) have respectiv e coaxial surfaces (28, 106A) adjacent to and spaced from one another and further have respective axial surfaces (46, 102) that frictionally engage on e another when the second assembly (96) is in a first axial position and disengage when the second assembly (96) is in a second axial position. The second assembly (96) is capable of rotation independent of the first assembl y (20) when the second assembly (90) is in the second axial position. The rotational control apparatus (10) includes an eddy current drive (132) comprised of a first eddy current coupling assembly (134) associated with th e coaxial surface (28) of the first assembly (20) and a second eddy current coupling assembly (136) associated with the coaxial surface (1 06A) of the second assembly (96), the second eddy current coupling assembly (136) adjace nt the first eddy current coupling assembly (134) with an air gap (114) therebetween.
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