| 摘要 |
Provided is an extension and retraction device for a telescopic boom, the extension and retraction device being configured so that the extension and retraction device is of low cost, can improve the operability of the telescopic boom, and can increase the efficiency of insertion work. An extension and retraction device (3) for a telescopic boom (1) is provided with: an extension and retraction cylinder (4) for extending and retracting a second boom (22); and an extension and retraction mechanism (5) for simultaneously extending and retracting a top boom (24) and a third boom (23) in coordination with the extension and retraction movement of the extension and retraction cylinder (4). The extension and retraction mechanism (5) is provided with a rod-shaped support member (10). The rod-shaped support member (10) is disposed within the top boom (24) with one end of the rod-shaped support member (10) affixed, within the third boom (23), to the base end side of the third boom (23). The rod-shaped support member (10) is formed in such a manner that sheaves (71, 71) for extending the top boom are provided within the top boom (24) and located on the front end side of the rod-shaped support member (10). |
