| 摘要 |
PROBLEM TO BE SOLVED: To reduce the cost required for the replacing work of a bit, and to secure the safety in the replacing work. SOLUTION: A shield excavator comprises a bit drum 12 arranged on the lines extended in the radial direction of an excavator body, a plurality of bit driving actuators which are arranged on the bit drum 12 in a row along the lines, and a plurality of pairs of bits 19a, 19b which are rotatably supported by the bit drive actuators around the axis parallel to the lines so that when one of the actuators is partly projected from an outer circumference of the bit drum 12, the other is located within the bit drum 12. |
