| 摘要 |
PURPOSE: A multi-step extension device of gondola arms is provided to obtain structural stability of arms by extending arms of each step by the same length and to avoid an accident by preventing displacement of arms when an extension drive chain is disconnected. CONSTITUTION: Arms have lower support rollers(21,31,41,51) and side guide rollers(22a,32a,42a,52a) in front ends, and the arms are combined with each other while less friction force is applied. At rear ends of the arms, upper support rollers(13,23,33,43), lower support rollers(14,24,34,44) and side guide brackets(10a,20a) are installed to make the arms extend with the arms of the other steps by sliding. With extension of arms(10,20,30,40) by the same length, structural instability due to unbalance driving of arms is avoided. When one of extension drive chains(15,25) is disconnected, contraction of arms is performed by contraction drive chains(16,26,36). Thus, unexpected movement of the arms is prevented.
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