A swivel-head drill bit has been invented for use in acquiring a sample of a possibly hard material at a predetermined depth. This mechanism is a simpler and thus potentially cheaper alternative to deep-coring and sampling mechanisms that contain secondary actuators to open doors and/or to drive internal sampling features. The only actuator needed to operate the swivel-head drill bit is the drill motor.
To be useful, a sampling mechanism must prevent mixing of sample material from the desired depth with material from other depths. Specifically, the present mechanism was developed subject to a requirement to limit mixing to a depth range of no more than 2 cm bracketing the desired depth. The challenge lay in satisfying this requirement without using secondary actuators.
The swivel-head drill bit includes (1) a body containing two identical sample chambers with openings at the front end capped by (2) the swivel head, which holds two cutters and can be rotated, relative to the body, to cover or uncover the openings. An integral shaft extends from behind the head through the body and is captured with a nut at the back end of the body. Small posts restrict the rotation of the head to a 90° range between the fully open and fully closed positions. The drill body and swivel head are made of MP35N alloy; the cutters are tungsten carbide inserts.
The head remains in the fully closed position as the drill bit is rotated clockwise during drilling. When the desired sampling depth has been reached, the bit is rotated counterclockwise, causing the head to swivel to the open position. The counterclockwise rotation is continued for a total of ten revolutions to move sample material into the sample chambers. Then the bit is rotated clockwise and pushed forward to swivel the head to the closed position. Finally, while rotating the bit clockwise slowly to keep the head in the closed position, the bit is withdrawn from the hole.
Swivel-head drill bits could be used to acquire subsurface samples from such diverse sources as geological sites, hazardous-waste dumps, structures, remote planets, comets, and asteroids. For example, they could be used to sample the walls and interiors of the Chernobyl nuclear reactors. In tests, the prototype swivel-head drill bit performed successfully in the acquisition of samples from the bottoms of holes in rock, plaster, and loose olivine sand.
This work was done by Greg R. Gillis-Smith of Caltech for NASA's Jet Propulsion Laboratory. NPO-20390