| 摘要 |
PURPOSE:To enhance the efficiency of excavation by providing a driver to vertically move side cutters set in plural vertical stages on both sides of a drill bit group and a switcher to switch a parallel longitudinal attitude to a widened width attitude or vice versa. CONSTITUTION:Under the condition that a drill bit 8 is rotationally operated and both side cutters 9 group is maintained at a vertical attitude, a prime mover 6 is actuated to turn a disc cam 15 integrated with a reverse shaft 2. A cam follower 16 is pushed up against a compressive spring 12 by the heaved portion 15a of the cam 15, and the cutters 9 group is raised. The heaved portion 15a passes through the cam follower 16, and the cutters 9 group is lowered by the force of the spring 12 to excavate a fixed width of trench. An oil- pressure cylinder 19 is operated, and while switching the cutters 9 group to a widened width attitude little by little, the cutters 9 group is moved vertically to excavate an expanded bottom trench. |
