| 摘要 |
An earth displacement drill is provided including a drill tube which can be driven for rotary movement and a boring tip connected thereto, wherein the boring tip has a cylindrical part which adjoins the drill tube and has at least two helical strips uniformly distributed around the circumference, which climb upwardly at a shallow angle, with the flat side of the strips preferably extending substantially parallel to the radius at the relevant position and in particular only over a fraction of the circumference of the cylindrical part. The boring tip also has a tapering part located beneath the cylindrical part and having at least two arched surfaces which are uniformly distributed around the tapering part. These arched surfaces expediently extend approximately parallel to the vertical and preferably more steeply than the helical strips. Moreover, they preferably extend only over a fraction of the periphery of the tapered part and terminate radially outwardly at least in the vicinity of the start of an associated helical strip. Such an earth displacement drill is improved in that the arched surfaces have lower edges which adjoin flat helical surfaces in a substantially step-free manner. The flat helical surfaces extend continuously to the lower edge of the cylindrical part and to the upper edge of the following arched surface as viewed opposite to the direction of rotation. The flat helical surfaces in each case form a step with the following arched surface as viewed opposite to the direction of rotation. |
