Method and apparatus for drilling in permafrost and the like

An article of manufacture, comprising:

• a. an earth auger consisting of helical flight which is affixed to the exterior of a central tube, with the upper end of the auger having means by which torque may be applied for rotating the auger, and the bottom end of the tube being open to present an exposed bore, so that the tube may internally receive an auxiliary earth-drilling mechanism in the form of a percussion hammer, with there being a thin annular space left between the hammer and the central tube, and further including at least one internal groove in the central tube near the bottom end thereof, and there being a sealing means in said groove to form a seal between the central tube and a percussion hammer which is installed in the tube, whereby cuttings generated in a hole being drilled can be prevented from working their way upward into the annular space between the central tube and the hammer;
• b. structural means located internally of the tube at the top end thereof for engaging the top end of a percussion hammer, and said means having a first passage for passing compressed air from an external source to the percussion hammer, and having a second passage for passing compressed air from an external source to the interior of the central tube but externally of the percussion hammer;
• and
• c. a plurality of vent holes extending through the sides of the central tube, such that air admitted to the annular space between a percussion hammer and the central tube may be vented through said holes, with at least some of the vent holes being downwardly inclined so as to create downwardly directed air jets as compressed air exists from said holes.

A drilling assembly which is particularly well adapted for drilling holes in the earth's crust, comprising:

• a. a relatively large earth auger consisting of at least one helical flight which is welded to a long central tube, with the upper end of the auger having means through which torque may be applied for rotating the same, with the auger having a given outer diameter and the tube having a given inner diameter, and the tube extending below the lower-most edge of a helical flight by about 8 inches;
• b. a downhole percussion hammer which is adapted to drive a drill bit axially and also to rotate the same, with the outer diameter of the percussion hammer being just slightly less than the inner diameter of the auger tube, whereby the percussion hammer may be suspended within the auger tube for operation therein;
• c. a substantially solid drill bit having a generally frustoconical shape, and the drill bit being connected such that it may be driven by the percussion hammer, with the drill bit being mounted ahead of the auger, and the diameter of the auger flight being at least 3 times the maximum diameter of the solid drill bit;
• and
• d. cutting means mounted on the lower end of the helical flight for cutting into the earth's crust when the auger is rotated about its longitudinal axis.