Drilling device; has inner rod, hollow outer rod and rotation device to rotate both rods, which drives drive wheel of outer rod and drive wheel of inner rod

摘要

The device has an inner rod (10), a hollow outer rod (17) and a rotation device (29) to rotate both rods. The rotation device drives a drive wheel (26) of the outer rod and a drive wheel (34) of the inner rod. The drive wheels may be driven in opposite directions and at differing speeds. Preferably, each drive wheel forms part of a gear (28,33), where the gears can be displaced relative to each other in the rod directions and are connected by a connecting shaft (35).