Unit for drilling bore hole in ground has driven tube with drill head - and liq. supply, and coaxial larger-dia. extendable return line to liq. reservoir raisable to vary liq. pressure in bore hole

摘要

The mechanism for drilling a bore hole in the ground comprises a tube with larger-dia. drilling head at its lower end provided with an opening to pass liq., a drive for the tube, and a pump to supply liq. to the tube interior. - A return for the liq. surrounds the tube and its lower end sealingly surrounds the bore hole at ground level whilst its upper end extends to a predetermined level above the ground, means being provided to adjust the height of the liq. column in the line above the liq. in the bore hole.