To miniaturize an apparatus and reduce its cost by making it movable at a speed synchronized with the movement of a formwork without bringing a tightening/loosening tool into contact with the formwork.
A carriage 10 having a nut runner 11 loaded thereon is set on an upper portion of the side of a formwork transferring cart 5. A bolt tightening/loosening starting position P1 and a carriage home position P2 are preset, and a transferring cart speed detecting sensor 7 and a bolt detecting sensor 13 are arranged in the vicinity close to the carriage home position P2. When the formwork transferring cart 5 starts to move and the bolt detecting sensor 13 detects a bolt, the time Tw when the bolt reaches the tightening/loosening starting position P1 is computed on the basis of the moving speed of the formwork transferring cart 5, and the starting time of the carriage 10 is decided by deducting time (t), which is required for the carriage 10 to reach the tightening/loosening starting position after starting from its home position, from the time Tw. When the starting time at the home position comes, the running of the carriage is started to catch up with the bolt which is tighten and loosen at the tightening/loosening starting position, and tightening/loosening work is carried out while the carriage is run at a synchronized speed. After finishing tightening/loosening work, the carriage is returned to its home position, and the subsequent tightening/loosening of a bolt is conducted by repeating the above-mentioned work.
NAGASAWA YOSHIFUMI
AYUSAWA KUNIHIKO
