| 摘要 |
<p>A rough terrain mobile crane in which the operator's control cab is mounted on a rotatable superstructure has all the controls grouped in the cab including a mechanical, preferably power assisted, steering system mechanically engageable when the cab is in a road travel position, an hydraulic steering system is alternatively engageable for on-site use and includes and separate directional control valve for steering road wheels on one of the axles, for example utilizing the power assisted part of the mechanical steering; the hydraulic system is water locked, or may free wheel when applied to the mechanically steered wheels, when not in use for road travel and four-wheel manoeuvering during craning operations in onsite use is provided without any occasion for undesirable build up of hydraulic pressure.</p> |
