| 摘要 |
A telescopic boom 9 comprises a proximal boom 9a, an intermediate boom 9b, and a distal boom 9c assembled together in a telescopic fashion. A telescopic cylinder 21 is disposed such that a distal end portion of a cylinder rod 21b is firmly attached to a proximal end portion of the proximal boom 9a, whereas a cylinder tube 21a is firmly attached into the intermediate boom 9b. A retraction sheave 25 is mounted to the cylinder tube 21a nearer the proximal end of the telescopic boom 9. An extension sheave 27 is mounted to the cylinder tube 21a nearer the distal end of the telescopic boom 9. A guide pipe 35 is disposed such that one end thereof is firmly attached to the proximal end portion of the proximal boom 9a and the other end is disposed between the retraction sheave 25 and the extension sheave 27. A protective tube 47 is disposed such that, with its one end firmly attached to the distal end portion of the guide pipe 35, it extends toward the distal end of the telescopic boom 9 and then is reversed in the vicinity of an end portion of the cylinder tube 21a so as to extend to a position opposing the guide pipe 35 from the cylinder tube 21a, with the other end connected to the proximal end portion of the distal boom 9c. A hose and the like 45 penetrate through the protective tube 47.
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