| 摘要 |
<p>In contrast to the prior art, the jibs, extendable and retractable on rollers, of a derrick of a goods-loading appliance supported on a motor vehicle have three solid longitudinal girders with one square cross-section and two rectangular cross-sections which are extended and retracted on roller sets. The axes of the rollers are arranged parallel to the surfaces of the longitudinal girders. This results in a considerable reduction in the longitudinal pressure acting on the rollers as well as considerable prolongation of their useful life. At the same time, the torsional strength of the jibs is increased and the adjustment or re-adjustment of the rollers is facilitated. <IMAGE></p> |
