| 摘要 |
PROBLEM TO BE SOLVED: To keep constant a distance between a workbench and an overhead electric wire without a boom operation by a workman even if height of the overhead electric wire changes. SOLUTION: A workbench lift control device 50 comprises a workbench contact strip device 51 and a controller 53. The workbench contact strip 51 abuts on an overhead electric wire installed above a rail, and comprises an abutting cylinder having an abutting member adapted to move vertically according to height of the overhead electric wire, and a pressure sensor 57 adapted to detect pressure acting on the abutting member from the overhead electric wire. The controller 53 comprises a pressure differential calculating circuit 63 adapted to calculate a difference between a detected pressure value of the pressure sensor 57 and a reference pressure, a memory 65 adapted to set up operating information of a valve 59 adapted to control operation of a derricking cylinder 21 corresponding to a calculated pressure differential, and an operation controlling circuit 61. Thereby, operation of a telescopic boom is controlled according to the operating information of a boom operating device 27 adapted to operate the telescopic boom, and operation of the valve 59 is controlled according to operating information of the valve 59.
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