ES384296A1 - Devices for connecting a drill bit to a drill string provided with a penetrometer - Google Patents

Abstract

Rotary drill is associated with a penetro meter for testing the soil, consisting of a probe 4 which may be pushed downwards through a central opening of the drill, and means (not described) for measuring the force required to insert the probe to a predetermined depth. The drill has a fixed bit 2 which leaves a central core 16 for the penetrometer, and a cutter 8 is provided to remove the core when the probe 4 is retracted. The cutter 8 (Fig. 1) is mounted on a pivot 7, and is swung inwards to cut the core, by, centrifugal force on a weight 6 the cutter is offset so that friction on the cutting edge urges the cutter inwards. When the drill is stopped, the cutter is swung outwards to clear the probe by a spring 11 connected to a balancing weight 9. The drill may also have nozzles 30 (Fig. 4) for jet drilling with the probe continuously extended. In this embodiment the cutter 8 is fixed to a vertical pivot 7 and a spring loaded piston 20 acts as a valve so that with a high drilling mud flow rate, it is forced downwards to close passages 23, so that the drilling and mud flows through the jet drilling nozzles 30. If the drill is rotating however, a projection 35 (Fig. 5, not shown) on the weight, projects an opening in the wall 18 to obstruct the piston. The drilling mud then flows also through passages 33, 31, a screen 32, and passages 38. Operation of the drill may be controlled by pressure pulses transmitted up the drill string through the drilling mud.