| 摘要 |
923,260. Collapsible mobile tower-cranes. ETABLISSEMENTS F. POTAIN & CIE. May 12, 1961 [May 18, 1960], No. 17363/61. Class 78 (4). As the tower 5a, Fig. 1, of a crane is raised into a vertical position the jib 7 is swung into a horizontal position by a member 11. As described, the member 11 is a cable, connected between a bracket 12 on a support 3 and a point 10 on a jib-carrying head 6, which tightens as the tower is raised by a winch 13. the part 5b of the tower telescopes within the part 5a. Two cables 11 may be provided, one on each side, or a single cable may be passed round two pulleys on the head 6, the ends being attached to the supports 3. In the embodiment shown in Fig. 6, a cable 11, which is initially taut, extends between points 10 and 12 and passes over pulleys 17, 18 mounted on the tower. In Fig. 9 a rigid strut 21 is connected between a pivot 20 on a bracket 19 on the jibcarrying bead 6 and a pivot 22 on the support 3, to form a parallel linkage with the tower. In a modification of this embodiment the strut 21 is arranged above the tower instead of below it when the tower is horizontal. In Fig. 11 the tower is mounted on brackets 3a and raised by a winch 13 and cable 14, a similar parallel link 21 being provided. In Fig. 12 a cable 11 which raises the jib does not form a parallel linkage with the tower. To compensate for this the cable 11 is wound on a subsidiary drum of a winch 24 which also raises the tower by means of a cable 14. |
