| 摘要 |
<p>A crane is operable in either a regular mode or a heavy duty mode. In the regular mode, an upper works is rotatable, through a turntable bearing, on a lower works. A boom is pivotally connected to one end of the upper works and a counterweight is connected to the opposite end thereof. In the heavy duty mode, a support ring surrounds the lower works and is connected thereto. An auxiliary frame is mounted on the support ring, surrounding the upper works, for rotation on the ring in unison with rotation of the upper works. The boom used in the regular mode is pivotally connected to the auxiliary frame for use as a gantry, and a heavier boom is pivotally connected to the auxiliary frame adjacent the gantry. The counterweight of the machine in the regular mode is shifted to the auxiliary frame opposite the boom and gantry, and an auxiliary counterweight is added to the auxiliary frame. -1a-</p> |
