| 摘要 |
A multisection extensible and retractable jib assembly is disclosed in this application. The jib assembly has a base section, at least one intermediate section and an outer section with means for extending and retracting the jib sections. The extending and retracting means includes a single cable having opposite ends connected to the outer section of the jib assembly and a reversible drive means operating with an intermediate portion of the cable and connected to the inner end of the base section of the jib assembly. A pair of pulleys are located on opposite ends of each intermediate section and one pulley is located on the outer end of the base section with the pulleys being positioned so that all of the cable portions between each pair of pulleys and the portion extending from the base section to the outer end section extends substantially parallel to each other and substantially parallel to the longitudinal axis of the jib assembly. |
