| 摘要 |
Aerial lifting equipment having a platform, a support structure and means rotatably mounting the support structure upon the platform for rotation about a substantially vertical axis. A boom structure is mounted on the support structure for movement about a substantially horizontal axis and drive means is mounted upon the platform and the support structure for causing rotation of the support structure about the vertical axis. The drive means includes a track structure mounted in a fixed position on the platform. The drive structure has a circular track surface and at least three spaced friction members adapted to engage the drive surface. Motive means is provided for driving at least one of the friction members. The motive drive means includes planetary gearing within one of the friction members. Preloading means is provided for applying preloading forces to the one friction drive member to yieldably urge it into engagement with the circular drive surface. Azimuth switch means is provided for preventing rotation of the support structure about the means rotatably mounting the same through more than a predetermined number of revolutions.
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