Steerably cutter for making underground duct for e g pipeline

摘要

The borer (1) has a directionally controllable thrust pipe (2) with a cutter (21) at its leading end mounted on a movable cylindrical shoe (20). The shoe outer surface (22) is matched to the thrust pipe outer diameter and concentric to the pipe axis (25), but the shoe inner surface is axially angled (alpha).A deflecting sleeve (27) within the shoe has a cylindrical inner surface (28) but an outer surface (29) angled (alpha) to the thrust pipe axis. A control pipe (5) within the thrust pipe can rotate the deflection sleeve to deflect the shoe by the angle of the shoe inner and the deflecting sleeve outer surface. This is done pref. by a cog (17) rotatably mounted on the control pipe acting on toothed strips (33,34) on the deflecting sleeve and thrust pipe respectively.