Drill for sinking concrete screw pile, has cutting screw blade with successive sections of increasing, constant and decreasing diameter in upward direction

摘要

The bottom end of the cutting screw blade comprise a section (4) that increases in diameter in the upward direction of the drill, before reaching a screw blade section (5) with a constant diameter, after which comes a screw blade section (6) with decreasing diameter. The cutter body comprises a tapered and optionally helical bottom part (1) with a diameter increasing in the upward direction, followed by a cylindrical section (2), after which comes a helical section (3) with decreasing diameter. At least one screw blade is provided around the cylindrical section and follows the same helical path as the cutter body. An independent claim is also included for a method for sinking a concrete screw-pile using this drill, comprising drilling into the ground in one direction and removing the drill by rotating it in the opposite direction whilst introducing concrete into the borehole via a channel in the drill. The drill tip is left behind at the bottom of the borehole when the drill is removed.