| 摘要 |
<p>PROBLEM TO BE SOLVED: To make a length detection action so as to be accurately performable with certainty and extending over a long period of time by protecting the measuring wire of a length detecting device from the outside. SOLUTION: A detector 18 of a length detecting device is set up in the base end of a lowermost stage boom body 7 in a boom body 6, and a measuring wire 17 drawn out of this detector 18 is passed through an inner part of the boom body 6 as guiding it with three guide members 23 and a guide pipe 24 in respective boom bodies 7 to 11 so as to prevent it from being damaged by contact with an external obstacle and rusted due to being exposed to wind and rain, in addition to corrosiveness and then the tip is locked to the topmost stage boom body 11.</p> |
