Four installation components which the husband Various are adhered by the top of the main pillar material of the four side which forms

摘要

PROBLEM TO BE SOLVED: To provide a derrick device to perform a high-efficient and smooth replacement work for the cross arm of a transmission steel tower. ;SOLUTION: By using a derrick device 1 of the top part of a steel tower 31, cross arms 32a are replaced on one side and another. An existing cross arm member cut and removed at an intermediate part is lifted down by a derrick device 1 and a newly arranging cross arm member is lifted up to effect a work. The derrick device 1 is assembled on a support frame 3. A mounting member 2 is fixed at the upper end part of a main column material 34 of the steel tower 31, the support frame 3 is caused to span and a main column material 34 is coupled thereto and the upper end part of the steel tower 31 is reinforced. A boom 4 is pivotally supported at the central part of a frame material. A lifting wire 10 is operated by a winch on a ground and a material is suspended by a boom 4. A pair of front legs 5 are pivotally supported at the two end parts of the frame material, and a pair of rear legs 6 are pivotally supported at the two end parts of the frame material. The upper ends of the front legs 5 and the rear legs 6 are pivotally supported at a coupling member. A wire 9 for regulating rise and fall of the boom 4 is locked to a winch for rise and fall on a ground.;COPYRIGHT: (C)1998,JPO