| 摘要 |
PROBLEM TO BE SOLVED: To hold a ground contact pressure for a drag head to the underwater floor in a standard ground contact pressure. SOLUTION: When the weight of a drag arm 2 increases after sucking of mud from the underwater floor, a tension of a wire 1 increases, a piston 51 is lowered, the contact pressure of the drag head 3 to the ground increases, and an air pressure in an air vessel 10 rises. An air pressure sensor 12 detects an air pressure change in the air vessel 10 and outputs it to a controller 9. The controller 9 supplies a predetermined electric current to a motor 8 based on the fluctuation in the air pressure. The rotating motion of the motor 8 is converted by a ball screw 7, and a piston 51 is pushed up. In this way, the drag head 3 is pulled and the contact pressure to the underwater floor can be recovered to the standard contact pressure to the ground.
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